 Section 35 of Gray's Anatomy, Part 4. 6A, the Posterior Divisions, Raymai Posterioris. The posterior divisions are as a rule smaller than the anterior. They are directed backward, and with the exceptions of those of the first cervical, the fourth and fifth sacral, and the coccygeal, divide into medial and lateral branches for the supply of the muscles and skin of the posterior part of the trunk. The Cervical Nerves, Nervei Cervicalis. The posterior division of the first cervical, or sub-oxcipital nerve, is larger than the anterior division and emerges above the posterior arch of the atlas and beneath the vertebral artery. It enters the sub-oxcipital triangle and supplies the muscles which bound this triangle, v's, the rectus capidus posterior major, and the obloquia superior and inferior. It gives branches also to the rectus capidus posterior minor and the semi-spinalus capidus. A filament from the branch to the obliquus inferior joins the posterior division of the second cervical nerve. The nerve occasionally gives off a cutaneous branch which accompanies the occipital artery to the scalp and communicates with the greater and lesser occipital nerves. The posterior division of the second cervical nerve is much larger than the anterior division and is the greatest of all the cervical posterior divisions. It emerges between the posterior arch of the atlas and the lamina of the axis below the obliquus inferior. It supplies a twig to this muscle, receives a communicating filament from the posterior division of the first cervical, and then divides into a large medial and a small lateral branch. The medial branch, ramus medialis, internal branch, called from its size and distribution the greater occipital nerve, nervous occipitalis major, great occipital nerve, ascends obliquely between the obliquus inferior and the semi-spinalus capidus and pierces the latter muscle and the trapezius near their attachments to the occipital bone. It is then joined by a filament from the medial branch of the posterior division of the third cervical, and ascending on the back of the head with the occipital artery divides into branches which communicate with the lesser occipital nerve and supply the skin of the scalp as far forward as the vertex of the skull. It gives off muscular branches to the semi-spinalus capidus and occasionally a twig to the back of the auricula. The lateral branch, ramus lateralis, external branch, supplies filaments to the spleenius, longest capidus, and semi-spinalus capidus, and is often joined by the corresponding branch of the third cervical. The posterior division of the third cervical is intermediate in size between those of the second and fourth. Its medial branch runs between the semi-spinalus capidus and servicis, and piercing the spleenius and trapezius ends in the skin. While under the trapezius it gives off a branch called the third occipital nerve, which pierces the trapezius and ends in the skin of the lower part of the back of the head. It lies medial to the greater occipital and communicates with it. The lateral branch often joins that of the second cervical. The posterior division of the suboccipital and the medial branches of the posterior division of the second and third cervical nerves are sometimes joined by communicating loops to form the posterior cervical plexus, cruveae. The posterior divisions of the lower five cervical nerves divide into medial and lateral branches. The medial branches of the fourth and fifth run between the semi-spinalus servicis and capidus, and having reached the spinous processes pierce the spleenius and trapezius to end in the skin. Sometimes the branch of the fifth fails to reach the skin. Those of the lower three nerves are small and end in the semi-spinalus servicis and capidus, multifidus and interspinales. The lateral branches of the lower five nerves supply the iliocostalus servicis, longissimus servicis, and longissimus capidus. The thoracic nerves nervei thoracalis. The medial branches, ramus medialis, internal branch, of the posterior divisions of the upper six thoracic nerves run between the semi-spinalus dorsi and multifidus, which they supply. They then pierce the rhomboidii and trapezius and reach the skin by the sides of the spinous processes. The medial branches of the lower six are distributed chiefly to the multifidus and longissimus dorsi. Occasionally they give off filaments to the skin near the middle line. The lateral branches, ramus lateralis, external branch, increase in size from above downward. They run through or beneath the longissimus dorsi to the interval between it and the iliocostalus and supply these muscles. The lower five or six also give off cutaneous branches which pierce the serratus posterior inferior and latimus dorsi and align with the angles of the ribs. The lateral branches of a variable number of the upper thoracic nerves also give filaments to the skin. The lateral branch of the 12th thoracic, after sending a filament medial word along the iliac crest, passes downward to the skin of the buttock. The medial cutaneous branches of the posterior divisions of the thoracic nerves descend for some distance close to the spinous processes before reaching the skin, while the lateral branches travel downward for a considerable distance. It may be as much as the breadth of four ribs before they become superficial. The branch from the 12th thoracic, for instance, reaches the skin only a little way above the iliac crest. The lumbar nerves, nervei lumbalis. The medial branches of the posterior divisions of the lumbar nerves run close to the articular processes of the vertebrae and end in the multifidus. The lateral branches supply the sacrospinalis. The upper three give off cutaneous nerves which pierce the aponeurosis of the latissimus dorsi at the lateral border of the sacrospinalis and descend across the posterior part of the iliac crest to the skin of the buttock, some of their twigs running as far as the level of the greater trochanter. The sacral nerves, nervei sacralis. The posterior divisions of the sacral nerves, ramiae posterioris, are small and diminishing size from above downward. They emerge, except the last, through the posterior sacral for ramina. The upper three are covered at their points of exit by the multifidus and divide into medial and lateral branches. The medial branches are small and end in the multifidus. The lateral branches join with one another and with the lateral branches of the posterior divisions of the last lumbar and fourth sacral to form loops on the dorsal surface of the sacrum. From these loops, branches run to the dorsal surface of the sacro tuberous ligament and form a second series of loops under the gluteus maximus. From this second series, cutaneous branches, two or three in number, pierce the gluteus maximus along a line drawn from the posterior superior iliac spine to the tip of the coccyx. They supply the skin over the posterior part of the buttock. The posterior divisions of the lower two sacral nerves are small and lie below the multifidus. They do not divide into medial and lateral branches, but unite with each other and with the posterior division of the coccygeal nerve to form loops on the back of the sacrum. Filaments from these loops supply the skin over the coccyx. The coccygeal nerve, nervous coccygeus. The posterior division of the coccygeal nerve, ramus posterior, does not divide into a medial and a lateral branch, but receives, as already stated, a communicating branch from the last sacral. It is distributed to the skin over the back of the coccyx. Section 36 of Gray's Anatomy. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Read by Morgan Scorpion. Anatomy of the Human Body Part 4 by Henry Gray. Posterior Divisions Part 1. 6b. The Anterior Divisions. Re mai anterioris. The anterior divisions of the spinal nerves supply the antrolateral parts of the trunk and the limbs. They are, for the most part, larger than the posterior divisions. In the thoracic region, they run independently of one another, but in the cervical, lumbar and sacral regions they unite near their origins to form flexuses. Nervous Cervicalis. The anterior divisions of the cervical nerves, Re mai anterioris, with the exception of the first, pass outward between the intertransversary anterior and posterior, lying on the grooved upper surfaces of the transverse processes of the vertebrae. The anterior division of the first, or suboccipital nerve, is used from the vertebral canal above the posterior arch of the atlas, and runs forward round the lateral aspect of its superior articular process, medial to the vertebral artery. In most cases it descends medial too and in front of the rectus capitis lateralis, but occasionally it pierces the muscle. The anterior divisions of the upper four cervical nerves unite to form the cervical flexus, and each receives a gray reymus communicans from the superior cervical ganglion of the sympathetic trunk. Those of the lower four cervical, together with the greater part of the first thoracic, form the brachial flexus. They each receive a gray reymus communicans, those for the fifth and sixth being derived from the middle, and those for the seventh and eighth from the lowest cervical ganglion of the sympathetic trunk. The cervical flexus. Plexus Cervicalis. The cervical flexus is formed by the anterior divisions of the upper four cervical nerves. Each nerve, except the first, divides into an upper and a lower branch, and the branches unite to form three loops. The flexus is situated opposite the upper four cervical vertebrae, in front of the levator scapulae and scalinus medius, and covered by the sternocleidomastoid deus. Its branches are divided into two groups, superficial and deep, and are here given in tabular form. The figures following the names indicate the nerves from which the different branches take origin. Superficial. Smaller occipital, 2C. Greater auricular, 2, 3C. Cutaneous cervical, 2, 3C. Supraclavicular, 3, 4C. Deep. Internal. Communicating. With hypoglossal, 1, 2C. With vagus, 1, 2C. With sympathetic, 1, 2, 3, 4C. Muscular. Vectus capitis lateralis, 1C. Vectus capitis anterior, 1, 2C. Longus capitis, 1, 2, 3C. Communicante cervicalis, 2, 3C. Frenic, 3, 4, 5C. Communicating with accessory, 2, 3, 4C. External. Muscular. Sternocleidomastoidaeus, 2C. Trapezius, 3, 4C. Levita scapulae, 3, 4C. Scalinus medius, 3, 4C. Superficial branches of the cervical plexus. The smaller occipital nerve, nervous occipitalis minor, small occipital nerve, arises from the second cervical nerve, sometimes also from the third. It curves around and ascends along the posterior border of the sternocleidomastoidaeus. Near the cranium, it perforates the deep fascia and is continued upward along the side of the head behind the auricular, supplying the skin and communicating with the greater occipital, the greater auricular, and posterior auricular branch of the facial. The smaller occipital varies in size and is sometimes duplicated. It gives off an auricular branch, which supplies the skin of the upper and back part of the auricular, communicating with the mastoid branch of the great auricular. This branch is occasionally derived from the greater occipital nerve. The great auricular nerve, nervous auricularis magnus, is the largest of the ascending branches. It arises from the second and third cervical nerves, winds around the posterior border of the sternocleidomastoidaeus, and, after perforating the deep fascia, ascends upon that muscle beneath the palletisma to the perotted gland, where it divides into an anterior and a posterior branch. The anterior branch, ramus anterior facial branch, is distributed to the skin of the face over the perotted gland and communicates in the substance of the gland with the facial nerve. The posterior branch, ramus posterior mastoid branch, supplies the skin over the mastoid process and on the back of the auricular, except at its upper part. A filament pierces the auricular to reach its lateral surface, where it is distributed to the lobule and lower part of the concha. The posterior branch communicates with the smaller occipital, the auricular branch of the vagus, and the posterior auricular branch of the facial. The cutaneous cervical, nervous cutaneous collie, superficial or transverse cervical nerve, arises from the second and third cervical nerves, turns around the posterior border of the sternocleidomastoidaeus about its middle and passing obliquely forward beneath the external jugular vein to the anterior border of the muscle, it perforates the deep cervical fascia and divides beneath the platysma into ascending and descending branches, which are distributed to the antrolateral parts of the neck. The ascending branches, ramus superioris, pass upward to the sub-maxillary region and form a plexus with the cervical branch of the facial nerve beneath the platysma. Others pierce that muscle and are distributed to the skin of the upper and front part of the neck. The descending branches, ramii inferioris, pierce the platysma and are distributed to the skin of the side and front of the neck as low as the sternum. The supraclavicular nerves, nervous supraclavicularis, descending branches, arise from the third and fourth cervical nerves. They emerge beneath the posterior border of the sternocleidomastoidaeus and descend in the posterior triangle of the neck beneath the platysma and deep cervical fascia. Near the cervical, they perforate the fascia and platysma to become cutaneous and are arranged, according to their position, into three groups, anterior, middle and posterior. The anterior supraclavicular nerves, nervous supraclavicularis anterioris, suprasternal nerves, cross obliquely over the external jugular vein and the clavicular and sternal heads of the sternocleidomastoidaeus and supply the skin as far as the middle line. They furnish one or two filaments to the sternoclavicular joint. The middle supraclavicular nerves, nervous supraclavicularis medii, supraclavicular nerves, cross the clavicle and supply the skin over the pectoralis major and deltoidaeus, communicating with the cutaneous branches of the upper intercostal nerves. The posterior supraclavicular nerves, nervous supraclavicularis posterioris, suprachromial nerves, pass obliquely across the outer surface of the trapezius and the equomian and supply the skin of the upper and posterior parts of the shoulder. Deep branches of the cervical plexus, internal series. The communicating branches consist of several filaments which pass from the loop between the first and second cervical nerves to the vagus, hypoglossal and sympathetic. The branch to the hypoglossal ultimately leaves that nerve as a series of branches, vis, the descending ramus, the nerve to the cyreohiodeus and the nerve to the geniohiodeus. A communicating branch also passes from the fourth to fifth cervical while each of the first four cervical nerves receives a gray ramus communicans from the superior cervical ganglion of the sympathetic. Muscular branches supply the longest capitas, rectus capitas anterior and rectus capitas lateralis. The communicante cervicalis, communicante's hypoglossi consist usually of two filaments, one derived from the second and the other from the third cervical. These filaments join to form the descendant cervicalis which passes downward on the lateral side of the internal jugular vein, crosses in front of the vein a little below the middle of the neck and forms a loop, ansa hypoglossi, with the descending ramus of the hypoglossal in front of the sheath of the carotid vessels. Occasionally the loop is formed within the sheath. The phrenic nerve, nervous phrenicus, internal respiratory nerve of Bell, contains motor and sensory fibres in the proportion of about two to one. It arises cheaply from the fourth cervical nerve but receives a branch from the third and another from the fifth. The fibres from the fifth occasionally come through the nerve to the subclavius. It descends to the root of the neck, running obliquely across the front of the scalenus anterior and beneath the sternocleidomastoid deus, the inferior belly of the omohiodaeus and the transverse cervical and transverse scapular vessels. It next passes in front of the first part of the subclavian artery, between it and the subclavian vein and, as it enters the thorax, crosses the internal mammary artery near its origin. Within the thorax it descends nearly vertically in front of the root of the lung and then between the pericardium and the medial steinal pleura to the diaphragm, where it divides into branches which pierce that muscle and are distributed to its undersurface. In the thorax it is accompanied by the pericardiacophrenic branch of the internal mammary artery. The two phrenic nerves differ in their length and also in their relations at the upper part of the thorax. The right nerve is situated more deeply and is shorter and more vertical in direction than the left. It lies lateral to the right inominate vein and superior vena cava. The left nerve is rather longer than the right from the inclination of the heart to the left side and from the diaphragm being lower on this than on the right side. At the root of the neck it is crossed by the thoracic duct. In the superior medial steinal cavity it lies between the left common carotid and left subclavian arteries and crosses superficial to the vagus on the left side of the artery aorta. Each nerve supplies filaments to the pericardium and pleura and at the root of the neck is joined by a filament from the sympathetic and occasionally by one from the anther hypoglossi. Branches have been described as passing to the peritoneum. From the right nerve one or two filaments pass to join in a small phrenic ganglion with phrenic branches of the cheliac plexus and branches from this ganglion are distributed to the falciform and coronary ligaments of the liver, the supra renal gland, inferior vena cava and right atrium. From the left nerve filaments pass to join the phrenic branches of the cheliac plexus but without any ganglionic enlargement and a twig is distributed to the left supra renal gland. Deep branches of the cervical plexus, external series, communicating branches. The external series of deep branches of the cervical plexus communicates with the accessory nerve in the substance of the sternocleidomastodeus in the posterior triangle and beneath the trapezius. Muscular branches are distributed to the sternocleidomastodeus trapezius, levitous scarpuli and scallionous medius. The branch for the sternocleidomastodeus is derived from the second cervical. The trapezius and levitous scarpuli receive branches from the third and fourth. The scallionous medius receive twigs either from the third or fourth or occasionally from both. The brachial plexus, plexus brachialis. The brachial plexus is formed by the union of the anterior divisions of the lower four cervical nerves and the greater part of the anterior division of the first thoracic nerve. The fourth cervical usually gives a branch to the fifth cervical and the first thoracic frequently receives one from the second thoracic. The plexus extends from the lower part of the side of the neck to the axilla. The nerves which form it are nearly equal in size, but their mode of communication is subject to some variation. The following is, however, the most constant arrangement. The fifth and sixth cervical unite soon after their exit from the intervertebral foramina to form a trunk. The eighth cervical and first thoracic also unite to form one trunk, while the seventh cervical runs out alone. Three trunks, upper, middle and lower, are thus formed, and as they pass beneath the clavicle, each splits into an anterior and a posterior division. Footnote. The posterior division of the lower trunk is very much smaller than the others and is frequently derived entirely from the eighth cervical nerve. End of footnote. The anterior divisions of the upper and middle trunks unite to form a cord, which is situated on the lateral side of the second part of the axillary artery and is called the lateral cord or fasciculus of the plexus. The anterior division of the lower trunk passes down on the medial side of the axillary artery and forms the medial cord or fasciculus of the brachial plexus. The posterior divisions of all three trunks unite to form the posterior cord or fasciculus of the plexus, which is situated behind the second portion of the axillary artery. Relations. In the neck, the brachial plexus lies in the posterior triangle, being covered by the skin, platysma and deep fascia. It is crossed by the supraclavicular nerves, the inferior belly of the omohiodaeus, the external jugular vein and the transverse cervical artery. It emerges between the scalini anterior and medius. Its upper part lies above the third part of the subclavian artery, while the trunk formed by the union of the eighth cervical and first thoracic is placed behind the artery. The plexus next passes behind the clavicle, the subclavius and the transverse scapular vessels and lies upon the first digitation of the serratus anterior and the subscapularis. In the axilla, it is placed lateral to the first portion of the axillary artery. It surrounds the second part of the artery, one cord lying medial to it, one lateral to it and one behind it. At the lower part of the axilla, it gives off its terminal branches to the upper limb. Branches of communication. Close to their exit from the intervertebral foramina, the fifth and sixth cervical nerves each receive a gray ramus communicans from the middle cervical ganglion of the sympathetic trunk and the seventh and eighth cervical, similar twigs from the inferior ganglion. The first thoracic nerve receives a gray ramus from and contributes a white ramus to the first thoracic ganglion. On the scalinus anterior, the phrenic nerve is joined by branches from the fifth cervical. Branches of distribution. The branches of distribution of the brachial plexus may be arranged into two groups. There's those given off above and those below the clavicle. Supraclavicular branches. Dorsal scapula, five C. Supraclavular, five C. Nerve to subclavius, five C. Long thoracic, five C. Toulongas colli and scalini, five C. End of section 36. Section 37 of Gray's Anatomy part four. This is a LibriVox recording. All LibriVox recordings are in a public domain. For more information or to volunteer, please visit LibriVox.org. Recording by M.L. Cohen. Anatomy to human body part four by Henry Gray. Anterior divisions of the spinal nerves, part two. The dorsal scapula nerve. Nervous dorsalus scapulae. Nerve to the rhomboidiae, posterior scapula nerve. Arises from the fifth cervical. Pierced to scalinus medius. Passes beneath the levator scapulae to which it occasionally gives a twig and ends in the rhomboidiae. The superscapular, nervous superscapularis, arises from the trunk formed by the union of the fifth and sixth cervical nerves. It runs lateral ward beneath the trapezius enomohiideus and enters the superspinatus fossa through the superscapular notch. Below, the superior transverse scapular ligament. It then passes beneath the superspinatus and curves around the lateral border of the spine of the scapulae to the infraspinatus fossa. In the superspinatus fossa, it gives off two branches to the superspinatus muscle and an articular filament to the solar joint. And in the infraspinatus fossa, it gives off two branches to the infraspinatus muscle besides some filaments to the solar joint and scapulae. The nerve to the subclavius, nervous subclavius is a small filament which arises from the point of junction of the fifth and sixth cervical nerves. It descends to the muscle in front of the third part of the subclavian artery and the lower trunk of the plexus and is usually connected by a filament with the phrenic nerve. The long thoracic nerve, nervous thoracalis longus, external respiratory nerve of Bell, posterior thoracic nerve, supplies the serratus anterior. It usually arises by three roots from the fifth, sixth, and seventh cervical nerves but the root from the seventh nerve may be absent. The roots from the fifth and sixth nerves pierce the scilliness medius while that from the seventh passes in front of the muscle. The nerve descends beneath the brachial plexus and the axillary vessels resting on the outer surface of the serratus anterior. It extends along the side of the thorax to the lower border of that muscle supplying filaments to each of its digitations. The branches for the longest coli and scillini arise from the lower four cervical nerves at their exit from the inter vertebral foramina. Infracolivicular branches. The infracolivicular branches are derived from the three cords of the brachial plexus but the fasciculi of the nerves may be traced through the plexus, to the spinal nerve from which they originate. They are as follows, musculocutaneous, fifth, sixth, and seventh cervical, lateral cord, lateral anterior thoracic, fifth, sixth, and seventh, lateral head of the median, sixth, and seventh, medial anterior thoracic, medial anterior to brachiocutaneous, sixth, and seventh, medial cord, medial brachiocutaneous, eighth cervical first thoracic, ulnar, medial head of median, also eighth cervical first thoracic, upper subscapular, fifth and sixth cervical, lower subscapular, fifth and sixth cervical. Postural cord, thoracodorsal, fifth, sixth, and seventh cervical, axillary, fifth and sixth cervical, radial, sixth, seventh, eighth cervical, first thoracic. The anterior thoracic nerves, nervous thoracalis anterioris, supply the pectoralis major and minor. The lateral anterior thoracic, fasciculus lateralis, the larger of the two arises from the lateral cord of the brachial plexus and through it from the fifth, sixth, and seventh cervical nerves. It passes around the axillary artery in vein, pierces the coricoclavicular fascia and is distributed to the deep surface of the pectoralis major. It sends a filament to join the medial anterior thoracic and form with it a loop in front of the first part of the axillary artery. The medial anterior thoracic, fasciculus medialis, arises from the medial cord of the plexus and through it from the eighth cervical and first thoracic. It passes behind the first part of the axillary artery, curves over between the axillary artery in vein and unites in front of the artery with a filament from the lateral nerve. It then enters the deep surface of the pectoralis minor where it divides into a number of branches which supply the muscle. Two or three branches pierce the muscle and end in the pectoralis major. The subscapular nerves, nervous subscapularis, to a number spring from the posterior cord of the plexus and through it from the fifth and sixth cervical nerves. The upper subscapular, short subscapular, the smaller enters the upper part of the subscapularis and is frequently represented by two branches. The lower subscapular supplies the lower part of the subscapularis and ends in the teres major. The latter muscle is sometimes applied by a separate branch. The thoracodorsal nerve, nervous thoracodorsalis, middle or long subscapular nerve. A branch of the posterior cord of the plexus derives its fibers from the fifth, sixth and seventh cervical nerves. It follows the course of the subscapular artery along the posterior wall of the axilla to the latissimus dorsi in which it may be traced as far as the lower border of that muscle. The axillary nerve, nervous axillaeris, circumflex nerve, arises from the posterior cord of the brachial plexus and its fibers are derived from the fifth and sixth cervical nerves. It lies at first behind the axilla artery and in front of the subscapularis and passes downward to the lower border of that muscle. It then winds backwards in company with the posterior humeral circumflex artery through a quadrilateral space bounded above by the subscapularis, below by the teres major, immediately by the long head of the triceps brachii and laterally by the surgical neck of the humerus and divides into an anterior and a posterior branch. The anterior branch, upper branch, buys around the cervical neck of the humerus beneath the deltoidius with the posterior humeral circumflex vessels as far as the anterior border of that muscle, supplying it and giving off a few small cutaneous branches which pierce the muscle and ramifying the skin covering its lower part. The posterior branch, lower branch, supplies the teres minor and the posterior part of the deltoidius. Upon the branch to the teres minor and oval enlargement, pseudo ganglion usually exists. The posterior branch then pierces deep fascia and is continued as the lateral brachial cutaneous nerve which sweeps around the posterior border of the deltoidius and supplies the skin over the lower two thirds of the posterior part of this muscle as well as that covering the long head of the triceps brachii. The trunk of the axillary nerve gives off an articular filament which enters the shoulder joint below the subscapularis. The musculocutaneous nerve, nervous musculocutaneous, arises from the lateral cord of the brachial plexus opposite the lower border of the prector allus minor. Its fiber is being derived from the fifth, sixth, and seventh cervical nerves. It pierces the carcobrachialis muscle and passes obliquely between the biceps brachii and the brachialis to the lateral side of the arm, a little above the elbow. It pierces the deep fascia lateral to the tendon of the biceps brachii and is continued into the forearm as the lateral anti-brachial cutaneous nerve. In its course through the arm, it supplies the carcobrachialis biceps brachii and the greater part of the brachialis. The branch to the carcobrachialis is given off from the nerve close to its origin and in some instances as a separate filament from the lateral cord of the plexus. It is derived from the seventh cervical nerve. The branches to the biceps brachii and brachialis are given off after the musculotanus as pierced carcobrachialis. That supplying the brachialis gives a filament to the elbow joint. The nerve also sends a small branch to the bone which enters the nutrient foramen with the accompanying artery. The lateral anti-brachial cutaneous nerve, nervous cutaneous anti-brachii, cutaneous lateralis, branched to the musculotanus nerve, passes behind the cephalic vein and divides opposite to elbow joint into a volar and dorsal branch. The volar branch, ramus folaris anterior branch, descends along the radial border of the forearm to the wrist and supplies the skin over the lateral half of its volar surface. At the wrist joint, it is placed in front of the radial artery and some filaments piercing the deep fascia accompanying that vessel to the dorsal surface of the carpus. The nerve then passes downward to the ball of the thumb where it ends in cutaneous filaments. It communicates with the superficial branch of the radial nerve and with the palmar cutaneous branch of the median nerve. The dorsal branch, ramus dorsalis posterior branch, descends along the dorsal surface of the radial side of the forearm to the wrist. It supplies the skin of the lower two thirds of the dorsal lateral surface of the forearm communicating with the superficial branch of the radial nerve and the dorsal anti-brachial cutaneous branch of the radial. The musculocutaneous nerve presents frequent irregularities. It may adhere for some distance to the median and then pass outward beneath the biceps brachii instead of through the coracle brachialis. Some of the fibers of the median may run for some distance in the musculocutaneous and then leave it to join their proper trunk. Less frequently, the reverse is the case and the median sends a branch to join the musculocutaneous. The nerve may pass under the coracle brachialis or through the biceps brachii. Occasionally, it gives a filament to the pronator teres and that supplies the dorsal surface of the thumb when the superficial branch of the radial nerve is absent. The medial anti-brachial cutaneous nerve. Nervous cutaneous anti-brachial medialis, internal cutaneous nerve, arises from the medial cord of the brachial plexus. It derives its fibers from the eighth cervical and first thoracic nerves and at its commencement, is placed medial to the axillary artery. It gives off near the axilla a filament which pierces the fascia and supplies the entanglement covering the biceps brachii nearly as far as the elbow. The nerve then runs down the ulnar side of the arm medial to the brachial artery, pierces the deep fascia with the bacillic vein about the middle of the arm and divides into a volar and an ulnar branch. The volar branch, ramus volaris anterior branch, the larger, passes usually in front of but occasionally behind the vena mediana cubitai, median bacillic vein. It then descends on the front of the ulnar side of the forearm, distributing filaments to the skin as far as the wrist and communicating with the palmar cutaneous branch of the ulnar nerve. The ulnar branch, ramus ularis posterior branch, passes obliquely downward on the medial side of the bacillic vein in front of the medial epicondyle of the humerus to the back of the forearm and then descends on its ulnar side as far as the wrist, distributing filaments to the skin. It communicates with the medial brachial cutaneous, the dorsal anti-brachial cutaneous branch of the radial and the dorsal branch of the ulnar. The medial brachial cutaneous nerve, nervous cutaneous brachii medialis, lesser internal cutaneous nerve, nerve of wristburg, is distributed to the skin on the ulnar side of the arm. It is the smallest branch of the brachial plexus and arising from the medial cord receives its fibers from the eighth cervical and first thoracic nerves. It passes through the axilla at first lying behind and then medial to the axillary vein and communicates with the intercostal brachial nerve. It descends along the medial side of the brachial artery to the middle of the arm where it pierces the deep fascia and is distributed to the skin of the back of the lower third of the arm, extending as far as the elbow where some filaments are lost in the skin in front of the medial epicondyle and others over the electronon. It communicates with the ulnar branch of the medial anti-brachial cutaneous nerve. In some cases, the medial brachial cutaneous and intercostal brachial are connected by two or three filaments which form a plexus in the axilla. In other cases, the intercostal brachial is of large size and takes the place of the medial brachial cutaneous receiving merely a filament of communication from the brachial plexus which represents the latter nerve. In a few cases, this filament is lacking. End of section 37. Section 38 of Gray's Anatomy part four. This is LibriVox recording. All LibriVox recordings are in the public domain for more information or to volunteer, please visit LibriVox.org. Recording by ML Cohen, Anatomy of the Human Body part four by Henry Gray, anterior divisions of the spinal nerves part three. The median nerve, nervous medianus, extends along the middle of the arm and forearm to the hand. It arises by two roots, one from the lateral and one from the medial core to the brachial plexus. These embrace the lower part of the axillary artery, uniting either in front of or lateral to that vessel. Its fibers are derived from the sixth, seventh, and eighth cervical and first thoracic nerves. As it descends through the arm, it lies at first lateral to the brachial artery. About the level of the insertion of the corgobrachialis, it crosses the artery, usually in front of but occasionally behind it and lies on the medial side at the bend of the elbow, where it is situated behind the laceratus fibrosis bycipital fascia and is separated from the elbow joint by the brachialis. In the forearm, it passes between the two heads of the pronator teres and crosses the ulnar artery but is separated from this vessel by the deep head of the pronator teres. It descends beneath the flexor digitorum sublimus, lying on the flexor digitorum profundus to within five centimeters of the transverse carpal ligament. Here it becomes more superficial and is situated between the tendons of the flexor digitorum sublimus and flexor carpal radialis. In this situation, it lies behind and rather to the radial side of the tendon of the palm roller slongus and is covered by the skin and fascia. It then passes behind the transverse carpal ligament into the palm of the hand. In its course, through the forearm, it is accompanied by the median artery, a branch of the volar interosseous artery. With the exception of the nerve to the pronator teres, which sometimes arises above the elbow joint, the median nerve gives off no branches in the arm. As it passes in front of the elbow, it supplies one or two twigs to the joint. In the forearm, its branches are muscular, volar interosseous and palmar. The muscular branches, rami muscularies, are derived from the nerve near the elbow and supply all of the superficial muscles on front of the forearm, except the flexor carpal ulnaris. The volar interosseous nerve, nervous interosseous anti-brakeobolaris anterior interosseous nerve, supplies the deep muscles on the front of the forearm except the ulnar half of the flexor digitorum profundus. It accompanies the volar interosseous artery along the front of the interosseous membrane in the interval between the flexor polisus longus and flexor digitorum profundus, supplying the whole of the former in the radial half of the ladder and ending below in the pronator quadratus and wrist joint. The palmar branch, rami musculaneous palmaris, nervous medianae of the median nerve, arises at the lower part of the forearm. It pierces the volar carpal ligament and divides into a lateral and a medial branch. The lateral branch supplies the skin over the ball of the thumb and communicates with the volar branch of the lateral anti-brakeocutaneous nerve. The median branch supplies the skin of the palm and communicates with the palmar cutaneous branch of the ulnar. In the palm of the hand, the median nerve is covered by the skin and the palmar aponeuroses and rests on the tendons of the flexor muscles. Immediately after emerging from under the transverse carpal ligament, the nerve becomes enlarged and flattened and splits into a smaller lateral and larger medial portion. The lateral portion supplies a short stout branch to certain of the muscles of the ball of the thumb, that is the abductor brevis, the opponent's and the super head of the flexor brevis and then divides into three proper volar digital nerves. Two of these supply the sides of the thumb while the third gives a twig to the third lumbar callus and is distributed to the radial side of the index finger. The medial portion of the nerve divides into two common volar digital nerves. The first of these gives a twig to the second lumbar callus and runs toward the cleft between the index and middle fingers, where it divides into two proper digital nerves for the adjoining side of these digits. The second runs towards the cleft between the middle and ring fingers and splits into two proper digital nerves for the adjoining sides of these digits. It communicates with a branch from the ulnar nerve and sometimes sends a twig to the third lumbar callus. Each proper digital nerve, opposite the base to the first phalanx, gives off a dorsal branch which joins the dorsal digital nerve from the superficial branch of the radial nerve and supplies the integument on the dorsal aspect of the last phalanx. At the end of the digit, the proper digital nerve divides into two branches, one of which supplies the pulp of the finger, the other ramifies around and beneath the nail. The proper digital nerves, as they run along the fingers, are placed superficial to the corresponding arteries. The ulnar nerve, nervous ulnaris, is placed along the medial side of the limb and is distributed to the muscles and skin of the forearm in hand. It arises from the medial cord of the brachial plexus and derives its fibers from the eighth cervical and first thoracic nerves. It is smaller than the median and lies at first behind it, but diverges from it in its course down the arm. At its origin, it lies medial to the axillary artery and bears the same relation to the brachial artery as far as the middle of the arm. Here, it pierces the medial intramuscular septum, rungs obliquely across the medial head of the triceps brachii and descends to the groove between the medial epicondyle and the lecranon, accompanied by the superior ulnar collateral artery. At the elbow, it rests upon the back of the medial epicondyle and enters the forearm between the two heads of the flexor carpi ulnaris. In the forearm, it descends along the ulnar side lying upon the flexor digitorum profundus. Its upper half is covered by the flexor carpi ulnaris. Its lower half lies on the lateral side of the muscle covered by the entanglement and fascia. In the upper third of the forearm, it is separated from the ulnar artery by a considerable interval, but in the rest of its extent lies close to the medial side of the artery. About five centimeters above the wrist, it ends by dividing into a dorsal and a volar branch. The branches of the ulnar nerve are articular to the elbow joint, muscular, palm arcutaneous, dorsal, and volar. The articular branches to the elbow joint are several small filaments which arise from the nerve as it lies in the groove between the medial epicondyle and the lecranon. The muscular branches, rami muscularis, two in number, arise near the elbow. One supplies the flexor carpi ulnaris. The other, the ulnar half of the flexor digitorum profundus. The palm arcutaneous branch, rami muscutaneous palm aris, arises about the middle of the forearm and descends on the ulnar artery giving off some filaments to the vessel. It perforates the volar carpal ligament and ends in the skin of the palm communicating with the palm arc branch of the medial nerve. The dorsal branch, rami mus dorsalis manis, arises about five centimeters above the wrist. It passes backward beneath the flexor carpi ulnaris, perforates the deep fascia and running along the ulnar side of the back of the wrist and hand divides into two dorsal digital branches. One supplies the ulnar side of the little finger. The other, the adjacent sides of the little and ring fingers. It also sends a twig to join that given by the superficial branch of the radial nerve for joining sides of the middle and ring fingers and assists in supplying them. A branch is distributed to the metacarpal region of the hand communicating with the twig of the superficial branch of the radial nerve. On the little finger, the dorsal digital branches extend only as far as the base of the terminal phalanx and on the ring finger as far as the base of the second phalanx. The more distal parts of these digits are supplied by dorsal branches derived from the proper volar digital branches of the ulnar nerve. The volar branch, rami mus volaris manis, crosses the transverse carpal ligament on the lateral side of the piece of form bone, medial and a little behind the ulnar artery. It ends by dividing into a superficial and a deep branch. The superficial branch, rami mus superficialis, nerve ulnaris, supplies the palmaris brevis and the skin on the owner's side of the hand and divides into a proper volar digital branch for the owner's side of the little finger and the common volar digital branch which gives a communicating twig to the median nerve and divides into two proper digital nerves for the joining sides of the little and ring fingers. The proper digital branches are distributed to the fingers in the same manner as those of the median. The deep branch, rami mus profundis, accompanied by the deep branch of the ulnar artery passes between the abductor digidae quinti and flexor digidae quinti brevis and then perforates the opponent's digidae quinti and follows the course of the deep volar arch beneath the flexor tendons. At its origin, it supplies the three short muscles of the little finger. As it crosses the deep part of the hand, it supplies it all the interocci and the third and fourth lumbar callies. It ends by supplying the adductoris polisis and the medial head of the flexor polisis brevis. It also sends articular filaments to the wrist joint. It has been pointed out that the ulnar part of the flexor digidae profundis is supplied by the ulnar nerve. The third and fourth lumbar callies, which are connected with the tendons of this part of the muscle, are supplied by the same nerve. In a like manner, the lateral part of the flexor digidae profundis and the first and second lumbar callies are supplied by the median nerve. The third lumbar callus frequently receives an additional twig from the median nerve. The radial nerve, nervous radialis musculos spiral nerve, the largest branch of the brachial plexus is the continuation of the posterior cord of the plexus. It's fibers are derived from the fifth, sixth, seventh and eighth cervical and first thoracic nerves. It descends behind the first part of the axillary artery and the upper part of the brachial artery and in front of the tendons of the latissimus dorsae and teres major. It then winds around from the medial to lateral side of the humerus in a groove with the arter profundae brachii between the medial and lateral heads of the triceps brachii. It pierces the lateral intermuscular septum and passes between the brachialis and brachior radialis to the front of the lateral epicondyle where it divides into a superficial and deep branch. The branches of the musculospiral nerve are muscular, superficial, cutaneous, deep. The muscular branches, ramus muscularis, supply the triceps brachii and conius brachior radialis extensor carpyr radialis longus and brachialis and are grouped as medial posterior and lateral. The medial muscular branches supply the medial and long heads of the triceps brachii. That to the medial head is a long slender filament which lies close to the ulnar nerve as far as the lower third of the arm and is therefore frequently spoken of as the ulnar collateral nerve. The posterior muscular branch of larcise arises from the nerve in the groove between the triceps brachii and the humerus. It divides into filaments which supply the medial and lateral heads of the triceps brachii and the anconius muscles. The branch for the lateral muscle is a long slender filament which descends in the substance of the medial head of the triceps brachii. The lateral muscular branches supply the brachior radialis, extensor carpyr radialis longus and the lateral part of the brachialis. The cutaneous branches are a two-in number, the posterior brachial cutaneous and the dorsal anti-brachial cutaneous. The posterior brachial cutaneous nerve nervous cutaneous brachii posterior internal cutaneous branch of musculospiral arises in the axilla with the medial muscular branch. It is of small size and passes through the axilla to the medial side of the area supplying the skin on its dorsal surface nearly as far as the electronon. In its course, it crosses behind and communicates with the intercostal brachial. The dorsal anti-brachial cutaneous nerve, nervous cutaneous anti-brachial dorsalis, external cutaneous branch in the musculospiral perforates the lateral head of the triceps brachii at its attachment to the humerus. The upper and smaller branch of the nerve passes to the front of the elbow lying close to the cephalic vein and supplies the skin of the lower half of the arm. The lower branch pierces the deep fascia below the insertion of the deltoidius and descends along the lateral side of the arm and elbow and then along the back of the forearm to the wrist supplying the skin in its course and joining near its termination with the dorsal branch of the lateral anti-brachial cutaneous nerve. The superficial branch of the radial nerve, ramus superficialis radial nerve, passes along the front of the radial side of the forearm to the commencement of its lower third. It lies at first slightly lateral to the radial artery concealed beneath the brachior radialis. In the middle third of the forearm, it lies behind the same muscle close to the lateral side of the artery. It quits the artery about seven centimeters above the wrist passes beneath the tendon of the brachior radialis and piercing the deep fascia divides into two branches. The lateral branch, the smaller, supplies the skin of the radial side and ball of the thumb joining with the volar branch of the lateral anti-brachial cutaneous nerve. The medial branch communicates above the wrist with the dorsal branch of the lateral anti-brachial cutaneous and on the back of the hand with the dorsal branch of the ulnar nerve. It then divides into four digital nerves which are distributed as follows. The first supplies the ulnar side of the thumb. The second, the radial side of the index finger. The third, the adjoining sides of the index and middle fingers. The fourth communicates with the filament from the dorsal branch of the ulnar nerve and supplies the adjacent sides of the middle and ring fingers. See footnote, footnote. According to Hutchison, the digital nerve to the thumb reaches only as high as the root of the nail. The one to the forefinger as high as the middle of the second phalanx and the one to the middle and ring fingers not higher than the first phalangeal joint. End footnote. The deep branch of the radial nerve. Nervous interosseous dorsalis, dorsal or posterior interosseous nerve winds to the back of the forearm around the lateral side of the radius between the two planes of fibers of the supinator and is prolonged downward between the superficial and deep layers of the muscles to the middle of the forearm. Considerably diminished in size, it descends as the dorsal interosseous nerve under interosseous membrane in front of the extensors policies longest to the back of the carpus where it presents a ganglia form enlargement from which filaments are distributed to the ligaments and articulations of the carpus. It supplies all the muscles on the radial side and dorsal surface of the forearm excepting the anconias, brachioradialis and extensor carpioradialis longus. End of section 38. Section 39 of Gray's Anatomy part four. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by Leanne Howlett. Anatomy of the Human Body, part four by Henry Gray, the thoracic nerves. Six C, the thoracic nerves, nerve I, thoracalis. The anterior divisions of the thoracic nerves and the rami anterioris, ventral divisions, are 12 in number on either side. 11 of them are situated between the ribs and are therefore termed intercostal. The 12th lies below the last rib. Each nerve is connected with the adjoining ganglion of the sympathetic trunk by a gray and a white ramus communicans. The intercostal nerves are distributed chiefly to the parietes of the thorax and abdomen and differ from the anterior divisions of the other spinal nerves in that each pursues an independent course, i.e. there is no plexus formation. The first two nerves supply fibers to the upper limb in addition to their thoracic branches. The next four are limited in their distribution to the parietes of the thorax. The lower five supply the parietes of the thorax and abdomen. The 12th thoracic is distributed to the abdominal wall and the skin of the buttock. The first thoracic nerve. The anterior division of the first thoracic nerve divides into two branches. One, the larger, leaves the thorax in front of the neck of the first rib and enters the brachial plexus. The other and smaller branch, the first intercostal nerve, runs along the first intercostal space and ends on the front of the chest as the first anterior cutaneous branch of the thorax. Occasionally, this anterior cutaneous branch is wanting. The first intercostal nerve as a rule gives off no lateral cutaneous branch, but sometimes it sends a small branch to communicate with the intercostal brachial. From the second thoracic nerve, it frequently receives a connecting twig which ascends over the neck of the second rib. The upper thoracic nerves, nerve I intercostalus. The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves and the small branch from the first thoracic are confined to the parietes of the thorax and are named thoracic intercostal nerves. They pass forward in the intercostal spaces below the intercostal vessels. At the back of the chest, they lie between the pleura and the posterior intercostal membranes, but soon pierced the ladder and run between the two planes of intercostal muscles as far as the middle of the rib. They then enter the substance of the intercostalus interni and running amidst their fibers as far as the costal cartilages. They gain the inner surfaces of the muscles and lie between them and the pleura. Near the sternum, they cross in front of the internal mammary artery and transversus thoracis muscle, pierce the intercostalus interni, the anterior intercostal membranes, and pectoralis major and supply the integument of the front of the thorax and over the mammum, forming the anterior cutaneous branches of the thorax. The branch from the second nerve unites with the anterior supraclavicular nerves of the cervical plexus. Branches, numerous slender muscular filaments supply the intercostalus, the subcostalus, the levatures casterum, the serratus posterior superior, and the transversus thoracis. At the front of the thorax, some of these branches cross the costal cartilages from one intercostal space to another. Lateral cutaneous branches, rami cutanii lateralis, are derived from the intercostal nerves about midway between the vertebrae and sternum. They pierce the intercostalus externi and serratus anterior and divide into anterior and posterior branches. The anterior branches run forward to the side and the four part of the chest, supplying the skin and the mammum. Those of the fifth and sixth nerves supply the upper digitations of the obliquus externus abdominis. The posterior branches run backward and supply the skin over the scapula and latissimus dorsi. The lateral cutaneous branch of the second intercostal nerve does not divide like the others into an anterior and a posterior branch. It is named the intercostal brachial nerve. It pierces the intercostalus externus and the serratus anterior, crosses the axilla to the medial side of the arm, and joins with a filament from the medial brachial cutaneous nerve. It then pierces the fascia and supplies the skin of the upper half of the medial and posterior part of the arm, communicating with the posterior brachial cutaneous branch of the radial nerve. The size of the intercostal brachial nerve is an inverse proportion to that of the medial brachial cutaneous nerve. A second intercostal brachial nerve is frequently given off from the lateral cutaneous branch of the third intercostal. It supplies filaments to the axilla and medial side of the arm. The lower thoracic nerves, the anterior divisions of the seventh, eighth, ninth, tenth, and eleventh thoracic nerves are continued anteriorly from the intercostal spaces into the abdominal wall. Hence they are named thoracicoabdominal intercostal nerves. They have the same arrangement as the upper ones as far as the anterior ends of the intercostal spaces, where they pass behind the costal cartilages and between the obliquus internus and transversus abdominis to the sheath of the rectus abdominis, which they perforate. They supply the rectus abdominis and end as the anterior cutaneous branches of the abdomen. They supply the skin of the front of the abdomen. The lower intercostal nerves supply their intercostalus and abdominal muscles. The last three send branches to the serratus posterior inferior. About the middle of their course, they give off lateral cutaneous branches. These pierce the intercostalus externi and the obliquus externus abdominis in the same line as the lateral cutaneous branches of the upper thoracic nerves and divide into anterior and posterior branches, which are distributed to the skin of the abdomen and back. The anterior branches supply the digitations of the obliquus externus abdominis and extend downward and forward nearly as far as the margin of the rectus abdominis. The posterior branches pass backward to supply the skin over the latissimus dorsi. The anterior division of the 12th thoracic nerve is larger than the others. It runs along the lower border of the 12th rib, often gives a communicating branch to the first lumbar nerve and passes under the lateral lumbocostal arch. It then runs in front of the quadratus lumborum, perforates the transversus and passes forward between it and the obliquus internus to be distributed in the same manner as the lower intercostal nerves. It communicates with the iliohypogastric nerve of the lumbar plexus and gives a branch to the pyramidalus. The lateral cutaneous branch of the last thoracic nerve is large and does not divide into an anterior and a posterior branch. It perforates the obliquus internus and externus, descends over the iliac crest in front of the lateral cutaneous branch of the iliohypogastric and is distributed to the skin of the front part of the gluteal region, some of its filaments extending as low as the greater trochanter. End of section 39, recording by Leanne Howlett. Section 40 of Gre's Anatomy, part four. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Rating by Bologna Times. Anatomy of the Human Body, part four by Henry Gray, the lumbosacral plexus. The lumbosacral plexus, plexus lumbosacralis. The anterior divisions of the lumbar, sacral and coxigil nerves form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the 12th thoracic. For descriptive purposes, this plexus is usually divided into three parts, the lumbar, sacral and pedundal plexuses. The lumbar nerves, nervus lumbales. The anterior divisions of the lumbar nerves, ramy anterioris, increase in size from above downward. They are joined near the origins by Gray Ramy, communicountes from the lumbar ganglia of the sympathetic trunk. These ramy consist of long slender branches which accompany the lumbar arteries around the sides of the vertebral bodies. Beneath the zoas major, their arrangement is somewhat irregular. One ganglion may give ramy to two lumbar nerves or one lumbar nerve may receive ramy from two ganglia. The first and second and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicountes. The nerves pass obliquely outward behind the zoas major or between its vesicule, distributing filaments to it and the quadratus lumborum. The first three and the greater part of the fourth are connected together in the situation by anesthetic loops and form the lumbar plexus. The smaller part of the fourth joins with the fifth to form the lumbosacral trunk which assists in the formation of the sacral plexus. The fourth nerve is named the nervus fricalis from the fact that it is subdivided between the two plexuses. The lumbar plexus, plexus lumbalis. The lumbar plexus is formed by the loops of communication between the anterior divisions of the first three and the greater part of the fourth lumbar nerves. The first lumbar often receives a branch from the last thoracic nerve. It is situated in the posterior part of the zoas major in front of the transverse processes of the lumbar vertebrae. The mode in which the plexus is arranged varies in different subjects. It differs from the brachial plexus in not forming an intricate interlacement but the several nerves of distribution arise from one or more of the spinal nerves in the following manner. The first lumbar nerve, frequently supplemented by a twig from the last thoracic, splits into an upper and lower branch. The upper and larger branch divides into the iliohypogastric and ilioinguinal nerves. The lower and smaller branch unites with a branch of the second lumbar to form the genitofemoral nerve. The remainder of the second nerve and the third and fourth nerves divide into ventral and dorsal divisions. The ventral division of the second unites with the ventral divisions of the third and fourth nerves to form the obiterator nerve. The dorsal divisions of the second and third nerves divide into two branches, a smaller branch from each uniting to form the lateral femoral cutaneous nerve and a larger branch from each joining with the dorsal division of the fourth nerve to form the femoral nerve. The accessory obiterator, when it exists, is formed by the union of two small branches given off from the third and fourth nerves. The branches of the lumbar plexus may therefore be arranged as follows. Iliohypogastric, first lumbar. Ilioinguinal, first lumbar. Ingenitofemoral, first second lumbar. Dorsal divisions, lateral femoral cutaneous, second and third lumbar. Femoral, second, third, fourth lumbar. Ventral divisions, obiterator, second, third and fourth lumbar. Accessory, obiterator, third and fourth lumbar. The iliohypogastric nerve, nervous iliohypogastricus arrives from the first lumbar nerve. It emerges from the upper part of the lateral border of the psoas major and crosses obliquely in front of the quadratus lumborum to the iliac crest. It then perforates the posterior part of the transversus abdominis near the crest of the ilium and divides between that muscle and the oblicus internus abdominis into a lateral and an anterior cutaneous branch. The lateral cutaneous branch, ramus cutaneous lateralis iliac branch pierces the obliquy internus and externus immediately above the iliac crest and is distributed to the skin of the gluteal region behind the lateral cutaneous branch of the last thoracic nerve. The size of this branch bears an inverse proportion to that of the lateral cutaneous branch of the last thoracic nerve. The anterior cutaneous branch, ramus cutaneous anterior hypogastric branch continues onward between the obliquus internus and transversus. It then pierces the obliquus internus, becomes cutaneous by perforating the aponeurosis of the obliquus externus about 2.5 centimeter above the subcutaneous inguinal ring and is distributed to the skin of the hypogastric region. The iliohypogastric nerve communicates with the last thoracic and ilioinguinal nerves. The ilioinguinal nerve, nervous ilioguinalis, smaller than the proceeding, arises with it from the first lumbar nerve. It emerges from the lateral border of the psoas major just below the iliohypogastric and passing obliquely across the quadratus lumbarum and iliacus. It perforates the transversus abdominis near the anterior part of the iliac crest and communicates with the iliohypogastric nerve between the transversus and the obliquus internus. The nerve then pierces the obliquus internus, distributing filaments to it and accompanying the spermatic cord through the subcutaneous inguinal ring is distributed to the skin of the upper and medial part of the thigh, to the skin over the root of the penis and upper part of the scrotum in the male and to the skin covering the mons pubis and labium magis in the female. The size of this nerve is in inverse proportion to that of the iliohypogastric. Occasionally, it is very small and ends by joining the iliohypogastric. In such cases, a branch from the iliohypogastric takes the place of the ilioinguinal or the lateral nerve may be altogether absent. The genitofemoral nerve, nervous genitofemoralis, genitocrural nerve, arises from the first and second lumbar nerves. It passes obliquely through the substance of the psoas major and emerges from its medial border close to the vertebral column, opposite the fibrocartilage between the third and fourth lumbar vertebrae. It then descends on the surface of the psoas major under cover of the peritoneum and divides into the external spermatic and lumboinguinal nerves. Occasionally, these two nerves emerge separately through the substance of the psoas. The external spermatic nerve, nervous spermaticus externus, genital branch of genitofemoral passes outward on the psoas major and pierces the fascia transversalis or passes through the abdominal inguinal ring. It then descends behind the spermatic cord to the scrotum, supplies the cremaster and gives a few filaments to the skin of the scrotum. In the female, it accompanies the round ligament of the uterus and is lost upon it. The lumboinguinal nerve, nervous lumboinguinalis femoral or creural branch of genitofemoral descends on the external iliac artery, sending a few filaments around it and passing beneath the inguinal ligament enters the sheath of the femoral vessels lying superficial and lateral to the femoral artery. It pierces the anterior layer of the sheath of the vessels and the fascia lata and supplies the skin of the anterior surface of the upper part of the thigh. On the front of the thigh, it communicates with the anterior cutaneous branches of the femoral nerve. A few filaments from the lumboinguinal nerve may be traced to the femoral artery. The lateral femoral cutaneous nerve, nervous cutaneous femoralis lateralis, external cutaneous nerve, arises from the dorsal divisions of the second and third lumbar nerves. It emerges from the lateral border of the psoas major about its middle and crosses the iliacus obliquely toward the anterior superior iliac spine. It then passes under the inguinal ligament and over the sartorius muscle into the thigh where it divides into two branches and anterior and a posterior. The anterior branch becomes superficial about 10 centimeters below the inguinal ligament and divides into branches which are distributed to the skin of the anterior and lateral parts of the thigh as far as the nape. The terminal filaments of this nerve frequently communicate with the anterior cutaneous branches of the femoral nerve and with the infra patellar branch of the saphenous nerve, forming with them the patellar plexus. The posterior branch pierces the fasciolata and subdivides into filaments which pass backward across the lateral and posterior surfaces of the thigh, supplying the skin from the level of the greatest trochanter to the middle of the thigh. The obturator nerve, nervous obturatoris, arises from the ventral divisions of the second third and fourth lumbar nerves. The branch from the third is the largest while that from the second is often very small. It descends through the fibers of the psoas major and emerges from its medial border near the brim of the pelvis. It then passes behind the common iliac vessels and on the lateral side of the hypochastric vessels and ureter which separated from the ureter and runs along the lateral wall of the lesser pelvis above and in front of the obturator vessels. To the upper part of the obturator foreman, here it enters the thigh and divides into an anterior and a posterior branch which are separated at first by some of the fibers of the obturator externus and lower down by the abductor brevis. The anterior branch, ramus anterior, leaves the pelvis in front of the obturator externus and descends in front of the adductor brevis and behind the pectinius and adductor longus. At the lower border of the latter muscle it communicates with the anterior cutaneous and saphenous branches of the femoral nerve forming a kind of plexus. It then descends upon the femoral artery to which it is finally distributed. Near the obturator foreman, the nerve gives off an articular branch to the hip joint. Behind the pectinius it distributes branches to the adductor longus and gracilis and usually to the adductor brevis and in rare cases to the pectinius. It receives a communicating branch from the accessory obturator nerve when that nerve is present. Occasionally the communicating branch to the anterior cutaneous and saphenous branches of the femoral is continued down as a cutaneous branch to the thigh and leg. When this is so, it emerges from beneath the lower border of the adductor longus, descends along the posterior margin of the sartorus to the medial side of the knee where it pierces the deep fascia, communicates with the saphenous nerve and is distributed to the skin of the tibial side of the leg as low down as its middle. The posterior branch, ramus posterior, pierces the anterior part of the obturator externus and supplies this muscle. It then passes behind the adductor brevis on the front of the adductor magnus where it divides into numerous muscular branches which are distributed to the adductor magnus and the adductor brevis when the latter does not receive a branch from the anterior division of the nerve. It usually gives off an articular filament to the knee joint. The articular branch for the knee joint is sometimes absent. It either perforates the lower part of the adductor magnus or passes through the opening which transmits the femoral artery and enters the popliteal fossa. It then descends upon the popliteal artery as far as the back part of the knee joint where it perforates the oblique popliteal ligament and is distributed to the synovial membrane. It gives filaments to the popliteal artery. The accessory obturator nerve, nervous obturatorius, accessorius, is present in about 29% of cases. It is of small size and arises from the ventral divisions of the third and fourth lumbar nerves. It descends along the medial border of the psoas major, crosses the superior ramus of the pubis and passes under the pectineus where it divides into numerous branches. One of these supplies the pectineus, penetrating its deep surface. Another is distributed to the hip joint while a third communicates with the anterior branch of the obturator nerve. Occasionally, the accessory obturator nerve is very small and is lost in the capsule of the hip joint. When it is absent, the hip joint receives two branches from the obturator nerve. The femoral nerve, nervous femoralis, anterior feral nerve. The largest branch of the lumbar plexus arises from the dorsal divisions of the second, third and fourth lumbar nerves. It descends through the fibers of the psoas major, emerging from the muscle at the lower part of its lateral border and passes down between it and the iliacus behind the iliac fascia. It then runs beneath the inguinal ligament into the thigh and splits into an anterior and a posterior division. Under the inguinal ligament, it is separated from the femoral artery by a portion of the psoas major. Within the abdomen, the femoral nerve gives off small branches to the iliacus and a branch which is distributed upon the upper part of the femoral artery. The latter branch may arise in the thigh. In the thigh, the anterior division of the femoral nerve gives off anterior cutaneous and muscular branches. The anterior cutaneous branches comprise the intermediate and medial cutaneous nerves. The intermediate cutaneous nerve, ramus cutaneous anterior, middle cutaneous nerve, pierces the fascia, elata, and generally the sartorus, about 7.5 centimeters below the inguinal ligament and divides into two branches which descend in immediate proximity along the forepart of the thigh to supply the skin as low as the front of the knee. Here they communicate with the medial cutaneous nerve and the infrapatellar branch of the saphenous to form the patellar plexus. In the upper part of the thigh, the lateral branch of the intermediate cutaneous communicates with the lumbo and guino branch of the genitofemoral nerve. The medial cutaneous nerve, ramus cutanus, ramus cutaneous anterior, internal cutaneous nerve, passes obliquely across the upper part of the sheath of the femoral artery and divides in front or at the medial side of that vessel into two branches an anterior and a posterior. The anterior branch runs downward on the sartorius, perforates the fascia, elata at the lower third of the thigh, and divides into two branches. One supplies the integument as low down as the medial side of the knee. The other crosses to the lateral side of the patellar, communicating in its course with the infrapatellar branch of the saphenous nerve. The posterior branch descends along the medial border of the sartorius muscle to the knee, where it pierces the fascia, elata, communicates with the saphenous nerve and gives off several cutaneous branches. It then passes down to supply the integument of the medial side of the leg. Beneath the fascia, elata, at the lower border of the adductor lungus, it joins to form a plexiform network. The plexiform network is a sub-sartorial plexus with branches of the saphenous and obturator nerves. When the communicating branch from the obturator nerve is large and continued to the integument of the leg, the posterior branch of the medial cutaneous is small and terminates in the plexus, occasionally giving off a few cutaneous filaments. The medial cutaneous nerve, before dividing, which pierces the fascia, elata to supply the integument of the medial side of the thigh, accompanying the lung saphenous vein. One of these filaments passes through the saphenous opening. A second becomes subcutaneous about the middle of the thigh. A third pierces the fascia at its lower third. Muscular branches, rame muscularis. The nerve to the pectaneous arises immediately below the inguinal ligament and passes behind the femoral sheath to enter the anterior surface of the muscle. It is often duplicated. The nerve to the sartorius arises in common with the intermediate cutaneous. The posterior division of the femoral nerve gives off the saphenous nerve and muscular and articular branches. The saphenous nerve, nervous saphenous, long or internal saphenous nerve, is the largest cutaneous branch of the femoral nerve. It approaches the femoral artery where this vessel passes beneath the sartorius and lies in front of it, behind the aponeurotic covering of the adductor canal, as far as the opening and the lower part of the adductor magnus. Here it quits the artery and emerges from behind the lower edge of the aponeurotic covering of the canal. It descends vertically along the medial side of the knee behind the sartorius, pierces the fascialata between the tendons of the sartorius and gracilus and becomes subcutaneous. The nerve then passes along the tibial side of the leg, accompanied by the great saphenous vein, descends behind the medial border of the tibia and, at the lower third of the leg, divides into two branches. One continues its course along the margin of the tibia and ends at the ankle. The other passes in front of the ankle and is distributed to the skin on the medial side of the foot, as far as the ball of the great toe, communicating with the medial branch of the superficial perineal nerve. Branches. The saphenous nerve, about the middle of the thigh, gives off a branch which joins the sub-sartorial plexus. At the medial side of the knee, it gives off a large infrapatellar branch, which pierces the sartorius and fascia, lata, and is distributed to the skin in front of the patella. This nerve communicates above the knee with the anterior cutaneous branches of the femoral nerve, below the knee, with other branches of the saphenous, and on the lateral side of the joint, with branches of the lateral femoral cutaneous nerve, forming a plexiform network, the plexus patella. The infrapatellar branch is occasionally small and ends by joining the anterior cutaneous branches of the femoral, which supply its place in front of the knee. Below the knee, the branches of the saphenous nerve are distributed to the skin of the front and medial side of the leg, communicating with the cutaneous branches of the femoral, or with filaments from the obturator nerve. The muscular branches supply the four parts of the quadriceps femoris. The branch to the rectus femoris enters the upper part of the deep surface of the muscle and supplies a filament to the hip joint. The branch to the vastus lateralis of large size accompanies the descending branch of the lateral femoral circumflex artery to the lower part of the muscle. It gives off an articular filament to the knee joint. The branch to the vastus medialis descends lateral to the femoral vessels in company with the saphenous nerve. It enters the muscle about its middle and gives off a filament, which can usually be traced downward on the surface of the muscle to the knee joint. The branches to the vastus intermedius, two or three in number, enter the anterior surface of the muscle about the middle of the thigh. A filament from one of these descends through the muscle to the articularis genio and the knee joint. The articular branch to the hip joint is derived from the nerve to the rectus femoris. The articular branches to the knee joint are three in number. One, a long slender filament is derived from the nerve to the vastus lateralis. It penetrates the capsule of the joint on its anterior aspect. Another, derived from the nerve to the vastus medialis, can usually be traced downward on the surface of this muscle to near the joint. It then penetrates the muscular fibers and accompanies the articular branch of the highest genicular artery, pierces the medial side of the articular capsule and supplies the synovial membrane. The third branch is derived from the nerve to the vastus intermedius. Footnote, note 135. In most cases, the fourth lumbar is the nervous percolis, but this arrangement is frequently departed from. The third is occasionally the lowest nerve which enters the lumbar plexus, giving at the same time some fibers to the sacral plexus and thus forming the nervous percolis. Or both the third and fourth may be fercal nerves. When this occurs, the plexus is termed high or prefixed. More frequently, the fifth nerve is divided between the lumbar and sacral plexuses and constitutes the nervous percolis. And when this takes place, the plexus is distinguished as a low or post-fixed plexus. These variations necessarily produce corresponding modifications in the sacral plexus. End footnote. End of section 40. Section 41 of Anatomy of the Human Body, Part 4. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Anatomy of the Human Body by Henry Gray, Part 4. The Sacral and Coxigial Nerves. Nervi, Sacralis, and Coxigius. The anterior divisions of the sacral and coxigial nerves, rami anterioris, form the sacral and pudental plexuses. The anterior divisions of the upper four sacral nerves enter the pelvis through the anterior sacral foramina, that of the fifth between the sacrum and coccyx, while that of the coxigial nerve curves forward below the rudimentary transverse process of the first piece of the coccyx. The first and second sacral nerves are large. The third, fourth, and fifth diminish progressively from above downward. Each receives a gray ramus communicans from the corresponding ganglion of the sympathetic trunk, while from the third and frequently from the second and the fourth sacral nerves, a white ramus communicans is given to the pelvic plexuses of the sympathetic. The sacral plexus, plexus sacralis. The sacral plexus is formed by the lumbosacral trunk, the anterior division of the first, and portions of the anterior divisions of the second and third sacral nerves. The lumbosacral trunk comprises the whole of the anterior division of the fifth, and a part of that of the fourth lumbar nerve. It appears at the medial margin of the psoace major, and runs downward over the pelvic brim to form the first sacral nerve. The anterior division of the third sacral nerve divides into an upper and a lower branch, the former entering the sacral and the latter, the pedental plexus. The nerves forming the sacral plexus converge toward the lower part of the greater sciatic foramen and unite to form a flattened band from the anterior and posterior surfaces of which several branches arise. The band itself is continued as the sciatic nerve, which splits on the back of the thigh into the tibial and common perineal nerves. These two nerves sometimes arise separately from the plexus, and in all cases, their independence can be shown by dissection. Relation. The sacral plexus lies on the back of the pelvis between the piriformis and the pelvic fascia. In front of it are the hypogastric vessels, the ureter, and the sigmoi colon. The superior gluteal vessels run between the lumbo sacral trunk and the first sacral nerve, and the inferior gluteal vessels between the second and third sacral nerves. All the nerves entering the plexus, with the exception of the third sacral, split into ventral and dorsal divisions, and the nerves arising from these are as follows. Nerve to quadratus femoris and gemellus inferior, ventral divisions, fourth and fifth lumbar, first sacral, nerve to obturator internus and gemellus superior, ventral divisions, fifth lumbar, first and second sacral. Nerve to piriformis, dorsal divisions, first and second sacral. Superior gluteal, dorsal divisions, fourth and fifth lumbar, first sacral. Inferior gluteal, dorsal divisions, fifth lumbar, first and second sacral. Posterior femoral cutaneous, ventral divisions, second and third sacral, dorsal divisions, first and second sacral. Sciatic tibial, ventral divisions, fourth and fifth lumbar, first, second and third sacral. Common peroneal, dorsal divisions, fourth and fifth lumbar, first and second sacral. The nerve to the quadratus femoris and gemellus inferior arises from the ventral divisions of the fourth and fifth lumbar and first sacral nerves. It leaves the pelvis through the greater sciatic foramen below the piriformis and runs down in front of the sciatic nerve. The gemelli and the tendon of the obturator internus and enters the anterior surfaces of the muscles. It gives an articular branch to the hip joint. The nerve to the obturator internus and gemellus superior arises from the ventral divisions of the fifth lumbar and first and second sacral nerves. It leaves the pelvis through the greater sciatic foramen below the piriformis and gives off the branch of the gemellus superior, which enters the upper part of the posterior surface of the muscle. It then crosses the ischial spine, reenters the pelvis through the lesser sciatic foramen and pierces the pelvic surface of the obturator internus. The nerve to the piriformis arises from the dorsal division of the second sacral nerve or the dorsal divisions of the first and second sacral nerves and enters the anterior surface of the muscle. This nerve may be double. The superior gluteal nerve, nervous gluteus superior, arises from the dorsal divisions of the fourth and fifth lumbar and first sacral nerves. It leaves the pelvis through the greater sciatic foramen above the piriformis, accompanied by the superior gluteal vessels and divides into a superior and an inferior branch. The superior branch accompanies the upper branch of the deep division of the superior gluteal artery and ends in the gluteus minimus. The inferior branch runs with the lower branch of the deep division of the superior gluteal artery across the gluteus minimus. It gives filaments to the glutea medius and minimus and ends in the tensor fascii lati. The inferior gluteal nerve, nervous gluteus inferior, arises from the dorsal divisions of the fifth lumbar and first and second sacral nerves. It leaves the pelvis through the greater sciatic foramen below the piriformis and divides into branches which enter the deep surface of the gluteus maximus. The posterior femoral cutaneous nerve, nervous cutaneous femoralis posterior, small sciatic nerve is distributed to the skin of the perineum and the posterior surface of the thigh and leg. It arises partly from the dorsal divisions of the first and second and from the ventral divisions of the second and third sacral nerves and issues from the pelvis through the greater sciatic foramen below the piriformis. It then descends beneath the gluteus maximus with the inferior gluteal artery and runs down the back of the thigh beneath the fascia lata and over the long head of the biceps femoris to the back of the knee. Here it pierces the deep fascia and accompanies the small syphenis vein to about the middle of the back of the leg. It's terminal twigs communicating with the sural nerve. Its branches are all cutaneous and are distributed to the gluteal region, the perineum and the back of the thigh and leg. The gluteal branches, nervi, cluneum inferioris, three or four in number turn upward around the lower border of the gluteus maximus and supply the skin covering the lower and lateral part of that muscle. The perineal branches, ramai perinealis, are distributed to the skin at the upper and medial side of the thigh. One long perineal branch inferior pudental, long scrotal nerve curves forward below and in front of the ischial tuberosity, pierces the fascia lata and runs forward beneath the superficial fascia of the perineum to the skin of the scrotum in the male and of the labium magis in the female. It communicates with the inferior hemorrhoidal and posterior scrotal nerves. The branches to the back of the thigh and leg consist of numerous filaments derived from both sides of the nerve and distributed to the skin covering the back and medial side of the thigh, the poplidio fossa and the upper part of the back of the leg. The sciatic, nervous ischiodicus, great sciatic nerve, supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh and those of the leg and foot. It is the largest nerve in the body, measuring two centimeters in breadth and is the continuation of the flat and band of the sacroplexus. It passes out of the pelvis through the greater sciatic foramen below the piriformis muscle. It descends between the greater trochanter of the femur and the tuberosity of the ischium and along the back of the thigh into about its lower third, where it divides into two large branches, the tibial and common perineal nerves. This division may take place at any point between the sacroplexus and the lower third of the thigh. When it occurs at the plexus, the common perineal nerve usually pierces the piriformis. In the upper part of its course, the nerve rests upon the posterior surface of the ischium, the nerve to the quadratus femoris, the obturator internus and gemeli and the quadratus femoris. It is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery and is covered by the gluteus maximus. Lower down, it lies upon the adductor magnus and is crossed obliquely by the long head of the biceps femoris. The nerve gives off articular and muscular branches. The articular branches, ramai articularis, arise from the upper part of the nerve and supply the hip joint, perforating the posterior part of its capsule. They are sometimes derived from the sacroplexus. The muscular branches, ramai muscularis, are distributed to the biceps femoris, semi-tendinosis, semi-membranosis and adductor magnus. The nerve to the short head of the biceps femoris comes from the common perineal part of the sciatic. While the other muscular branches arise from the tibial portion, as may be seen in those cases where there is a high division of the sciatic nerve. The tibial nerve and tibialis, internal popliteal nerve, the larger of the two terminal branches of the sciatic, arises from the anterior branches of the fourth and fifth lumbar and first, second and third sacral nerves. It descends along the back of the thigh and through the middle of the popliteal fossa to the lower part of the popliteus muscle where it passes with the popliteal artery beneath the arch of the soleus. It then runs along the back of the leg with the posterior tibial vessels to the interval between the medial malleolus and the heel where it divides between the laciniate ligament into the medial and lateral plantar nerves. In the thigh, it is overlapped by the hamstring muscles above and then becomes more superficial and lies lateral to and some distance from the popliteal vessels. Opposite the knee joint, it is in close relation with these vessels and crosses to the medial side of the artery. In the leg, it is covered in the upper part of its course by the muscles of the calf, lower down by the skin, the superficial and deep fascia. It is placed on the deep muscles and lies at first to the medial side of the posterior tibial artery but soon crosses that vessel and descends on its lateral side as far as the ankle. In the lower third of the leg, it runs parallel with the medial margin of the tendo calcinius. The branches of this nerve are articular, muscular, medial, sural, cutaneous, medial, calcinial, medial and lateral plantar. Articular branches, ramiarticularis, usually three in number, supply the knee joint. Two of these accompany the superior and inferior medial genicular arteries and a third, the middle genicular artery. Just above the bifurcation of the nerve, an articular branch is given off to the ankle joint. Muscular branches, ramiarticularis, four or five in number, arise from the nerve as it lies between the two heads of the gastrocnemius muscle. They supply that muscle and the plantaris, soleus and puplidius. The branch for the puplidius turns around the lower border and is distributed to the deep surface of the muscle. Lower down, muscular branches arise separately or by a common trunk and supply the soleus, tibialis posterior, flexor digitorum longus and flexor helusus longus. The branch to the last muscle accompanies the perineal artery that to the soleus enters the deep surface of the muscle. The medial sural cutaneous nerve, nervous cutaneous suri medialis, nervous q-manicans tibialis, descends between the two heads of the gastrocnemius and about the middle of the back of the leg pierces the deep fascia and unites with the anesthmatic ramus of the common perineal to form the sural nerve. The sural nerve, nervous cerealis short saphenous nerve, formed by the junction of the medial sural cutaneous with the perineal anesthmatic branch passes downward near the lateral margin of the tendocalcaneus lying close to the small saphenous vein to the interval between the lateral malleolus and the calcaneus. It runs forward below the lateral malleolus and is continued as the lateral dorsal cutaneous nerve along the lateral side of the foot and little toe, communicating on the dorsum of the foot with the intermediate dorsal cutaneous nerve, a branch of the superficial perineal. In the leg, it's branches communicate with those of the posterior femoral cutaneous. The medial calcaneal branches, ramai calcanei medialis, internal calcaneal branches, perforate the laciniate ligament and supply the skin of the heel and medial side of the sole of the foot. The medial plantar nerve, nervous plantarus medialis, internal plantar nerve, the larger of the two terminal divisions of the tibial nerve accompanies the medial plantar artery. From its origin under the laciniate ligament, it passes under the cover of the abductor halusis. And appearing between this muscle and the flexor digitorum brevis gives off a proper digital plantar nerve and finally divides opposite the bases of the metatarsal bones into three common digital plantar nerves. Branches. The branches of the medial plantar nerve are, one, cutaneous, two, muscular, three, articular, four, a proper digital nerve to the medial side of the great toe and five, three common digital nerves. The cutaneous branches pierce the plantar aponeurosis between the abductor halusis and the flexor digitorum brevis and are distributed to the skin of the sole of the foot. The muscular branches supply the abductor halusis, the flexor digitorum brevis, the flexor halusis brevis, and the first lumbriculus. Those for the abductor halusis and flexor digitorum brevis arise from the trunk of the nerve near its origin and enter the deep surfaces of the muscles. The branch of the flexor halusis brevis springs from the proper digital nerve to the medial side of the great toe and that for the first lumbriculus from the first common digital nerve. The articular branches supply the articulations of the tarsus and meditarsus. The proper digital nerve of the great toe, nervi digitalis plantaris propriae, plantar digital branches, supplies the flexor halusis brevis and the skin on the medial side of the great toe. The three common digital nerves, nervi digitalis plantaris communes, pass between the divisions of the plantar aponeurosis and each splits into two proper digital nerves. Those of the first common digital nerve supply the adjacent sides of the great and second toes. Those of the second, the adjacent sides of the second and third toes and those of the third, the adjacent sides of the third and fourth toes. The third common digital nerve receives a communicating branch from the lateral plantar nerve. The first gives a twig to the first lumbriculus. Each proper digital nerve gives off cutaneous and articular filaments and opposite the last phalanx sends upward a dorsal branch which supplies the structures around the nail, the continuation of the nerve being distributed to the ball of the toe. It will be observed that these digital nerves are similar in their distribution to those of the median nerve in the hand. The lateral plantar nerve, nervi plantaris lateralis external plantar nerve supplies the skin of the fifth toe and lateral half of the fourth as well as most of the deep muscles. Its distribution being similar to that of the ulnar nerve in the hand. It passes obliquely forward with the lateral plantar artery to the lateral side of the foot lying between the flexor digitorum brevis and the quadratus plantae and in the interval between the former muscle and the abductor digiti quintae divides into a superficial and a deep branch. Before its division it supplies the quadratus plantae and abductor digiti quintae. The superficial branch, remus superficialis splits into a proper and a common digital nerve. The proper digital nerve supplies the lateral side of the little toe, the flexor digiti quintae brevis and the two interosseae of the fourth intermetotarsal space. The common digital nerve communicates with the third common digital branch of the medial plantar nerve and divides into two proper digital nerves which supply the adjoining sides of the fourth and fifth toes. The deep branch, remus profundus muscular branch accompanies the lateral plantar artery on the deep surface of the tendons of the flexor muscles and the adductor helusis and supplies all the interosseae except those in the fourth metotarsal space, the second, third and fourth lumbricules and the adductor helusis. End of section 41.