 Section 51 of Grey's Anatomy Part 4. The ciliares muscle, muscular ciliares, Roman's muscle, consists of unstriped fibres. It forms a grayish, semi-transparent circular band about three millimetres broad on the outer surface of the forepart of the coroid. It is thickest in front and consists of two sets of fibres, meridional and circular. The meridional fibres, much the more numerous, arise from the posterior margin of the scleral spur. They run backward and are attached to the ciliary processes and orbiculus ciliares. One bundle, according to Waldyer, is inserted into the sclerar. The circular fibres are internal to the meridional ones, and in a meridional section appear as a triangular zone behind the filtration angle and close to the circumference of the iris. They are well developed in hypometropic, but are rudimentary or absent in myopic eyes. The ciliares muscle is the chief agent in accommodation, i.e., in adjusting the eye to the vision of near objects. When it contracts, it draws forward the ciliary processes, relaxes the suspensory ligament of the lens, and thus allows the lens to become more convex. The iris. The iris has received its name from its various colours in different individuals. It is a thin, circular, contractile disc, suspended in the aqueous humour between the cornea and the lens, and perforated a little to the nasal side of its centre by a circular aperture, the pupil. By its periphery it is continuous with the ciliary body, and is also connected with the posterior elastic lamina of the cornea by means of the pectinate ligament. Its surfaces are flattened, and look forward and backward. The anterior toward the cornea, the posterior toward the ciliary processes and lens. The iris divides the space between the lens and the cornea into an anterior and a posterior chamber. The anterior chamber of the eye is bounded in front by the posterior surface of the cornea, behind by the front of the iris and the central part of the lens. The posterior chamber is a narrow chink behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes. In the adult the two chambers communicate through the pupil, but in the fetus up to the seventh month they are separated by the membrana pupilaris. Structure The iris is composed of the following structures. One In front is a layer of flattened endothelial cells placed on a delicate hyaline basement membrane. This layer is continuous with the endothelium covering the posterior elastic lamina of the cornea, and in individuals with dark coloured irides, the cells contain pigment granules. Two The stroma, stroma irides of the iris, contains the fibres and cells. The former are made up of delicate bundles of fibres tissue. A few fibres at the circumference of the iris have a circular direction, but the majority radiate toward the pupil, forming by their interlacement, delicate meshes, in which the vessels and nerves are contained. Interspersed between the bundles of connective tissue are numerous branched cells with fine processes. In dark eyes, many of them contain pigment granules, but in blue eyes, and the eyes of albinos they are unpigmented. Three The muscular fibres are involuntary and consist of circular and radiating fibres. The circular fibres form the sphincter pupuli. They are arranged in a narrow band about one millimetre in width which surrounds the margin of the pupil toward the posterior surface of the iris. Those near the free margin are closely aggregated. Those near the periphery of the band are somewhat separated and form incomplete circles. The radiating fibres form the dilator pupuli. They converge from the circumference toward the centre, and blend with the circular fibres near the margin of the pupil. Four The posterior surface of the iris is of a deep purple tint, being covered by two layers of pigmented columnar epithelium, continuous at the periphery of the iris with the palstyliaris retinae. This pigmented epithelium is named the palz iridica retinae, or from the resemblance of its colour to that of a ripe grape, the urea. The colour of the iris is produced by the reflection of light from dark pigment cells underlying a translucent tissue, and is therefore determined by the amount of the pigment and its distribution throughout the texture of the iris. The number and situation of the pigment cells differ in different irides. The albino pigment is absent. In the various shades of the blue eyes, the pigment cells are confined to the posterior surface of the iris, whereas in grey, brown and black eyes, pigment is found also in the cells of the stroma and in those of the endothelium on the front of the iris. The iris may be absent, either in part or altogether as a congenital condition, and in some instances the pupillary membrane may remain persistent, though it is rarely complete. Again, the iris may be the seat of a malformation, termed coloboma, which consists in a deficiency or cleft, clearly due in great number of cases to an arrest in development. In these cases the cleft is found at the lower aspect, extending directly downward from the pupil, and the gap frequently extends to the chloride to the porous opticus. In some rarer cases the gap is found in other parts of the iris, and is not then associated with any deficiency of the chloride. Vessels and Nerves The arteries of the iris are derived from the long and anterior ciliary arteries and from the vessels of the ciliary processes. Each of the two long ciliary arteries, having reached the attached margin of the iris, divides into an upper and lower branch. These anastomores with corresponding branches from the opposite side, and thus encircle the iris. Into this vascular circle, circular arteriosus major, the anterior ciliary arteries pour their blood and from it vessels converge to the free margin of the iris, and there communicate and form a second circle, circular arteriosus minor. The nerves of the chloride and iris are the long and short ciliary, the former being branches of the nasal ciliary nerve, the latter of the ciliary ganglion. They pierce the square around the entrance of the optic nerve, run forward in the pericoroidal space, and supply the blood vessels of the chloride. After reaching the iris, they form a plexus around its attached margin. From this are derived non-medulated fibres which end in the sphincter and dilator pupuli. Their exact mode of termination has not been ascertained. Other fibres from the plexus end in a network on the anterior surface of the iris. The fibres derived to the motor root of the ciliary ganglion from the ocular motor nerve supply the sphincter, while those derived from the sympathetic supply the dilator. Membrana pupularis. In the fetus, the pupil is closed by a delicate vascular membrane, the membrane pupularis, which divides the space in which the iris is suspended into two distinct chambers. The vessels of this membrane are partly derived from those of the margin of the iris, and partly from those of the capsule of the lens. They have a looped arrangement and converge towards each other without anastomosing. About the sixth month, the membrane begins to disappear by absorption from the centre towards the circumference, and at birth only a few fragments are present. In exceptional cases it persists. The retina, tunica interna. The retina is a delicate nervous membrane upon which the images of external objects are received. Its outer surface is in contact with the choroid, its inner with the hyaloid membrane of the vitreous body. Behind it is continuous with the optic nerve. It gradually diminishes in thickness from behind forward and extends nearly as far as the ciliary body, where it appears to end in a jagged margin, the auras serata. Here the nervous tissues of the retina end, but a thin prolegation of the membrane extends forward over the back of the ciliary processes and iris, forming the parcelliaris retinae, and past iridica retinae already referred to. This forward prolegation consists of the pigmentary layer of the retina together with the stratum of columnar epithelium. The retina is soft, semi-transparent, and of a purple tint in the fresh state, owing to the presence of a colouring material named rhodopsin or visual purple, but it soon becomes clouded, opaque, and bleached when exposed to sunlight. Immediately in the centre of the posterior part of the retina, corresponding to the axis of the eye, and at a point in which the sense of vision is most perfect, is an oval yellowish area, the macular lutea. In the macula is a central depression, the phobia centralis. At the phobia centralis the retina is exceedingly thin, and the dark colour of the cooid is distinctly seen through it. About three millimetres to the nasal side of the macular lutei is the entrance of the optic nerve. Optic disc. The circumference of which is slightly raised to form an eminence, colliculus nervi optici. The arteria centralis retinae pierces the centre of the disc. This is the only part of the surface of the retina which is insensitive to light, and it is termed the blind spot. Structure The retina consists of an outer pigmented layer and an inner nervous stratum or retina proper. The pigmented layer consists of a single stratum of cells. When viewed from the outer surface these cells are smooth and hexagonal in shape. When seen in section each cell consists of an outer non-pigmented part containing a large oval nucleus and an inner pigmented portion which extends as a series of straight thread-like processes between the rods, this being especially the case when the eye is exposed to light. In the eyes of albinos the cells of this layer are destitute of pigment. Retina proper The nervous structures of the retina proper are supported by a series of non-nervous or sustentacular fibres, and when examined microscopically by means of sections made perpendicularly to the surface of the retina are found to consist of seven layers named from within outward as follows. 1. Stratum opticum 2. Ganglionic layer 3. Inner plexiform layer 4. Inner nuclear layer or layer of inner granules 5. Outer plexiform layer 6. Outer nuclear layer or layer of outer granules 7. Layer of rods and cones 1. The stratum opticum or layer of nerve fibres is formed by the expansion of the fibres of the optic nerve. It is thickest near the porous opticus, gradually diminishing toward the aura serata. As the nerve fibres pass through the lamina cribrosus scleri, they lose their medullary sheaths and are continued onward through the coroid and retina as simple axis cylinders. When they reach the internal surface of the retina they radiate from their point of entrance over this surface grouped in bundles, and in many places arranged in plexuses. Most of the fibres are centripetal and are the direct continuations of the axis cylinder processes of the cells of the ganglionic layer, but a few of them are centrifugal and ramify in the inner plexiform and inner nuclear layers where they end in enlarged extremities. 2. The ganglionic layer consists of a single layer of large ganglion cells except in the macular lutea where there are several strata. The cells are somewhat flask shaped, the rounded internal surface of each resting on the stratum opticum, and sending up an axon which is prolonged into it. From the opposite end numerous dendrites extend into the inner plexiform layer where they branch and form flattened arborizations at different levels. The ganglion cells vary much in size and the dendrites of the smaller ones as a rule arborize in the inner plexiform layer as soon as they enter it, while those of the larger cells ramify close to the inner nuclear layer. 3. The inner plexiform layer is made up of a dense reticulum of minute fibrils formed by the interlacement of the dendrites of the ganglion cells with those of the cells of the inner nuclear layer. Within this reticulum a few branch spongioblasts are sometimes embedded. 4. The inner nuclear layer or layer of inner granules is made up of a number of closely packed cells of which there are three varieties, Viz, bipolar cells, horizontal cells and amachrine cells. The bipolar cells by far the most numerous are round or oval in shape and each is prolonged into an inner and an outer process. They are divisible into rod bipolar and cone bipolar. The inner processes of the rod bipolar run through the inner plexiform layer and arborize around the bodies of the cells of the ganglionic layer. Their outer processes end in the outer plexiform layer in tufts of fibrils around the button-like ends of the inner processes of the rod granules. The inner processes of the cone bipolar ramify in the inner plexiform layer in contact with the dendrites of the ganglionic cells. The horizontal cells lie in the outer part of the inner nuclear layer and possess somewhat flattened cell bodies. Their dendrites divide into numerous branches in the outer plexiform layer while their axons run horizontally for some distance and finally ramify in the same layer. The amachrine cells are placed in the inner part of the inner nuclear layer and are so named because they have not yet been shown to possess axis cylinder processes. Their dendrites undergo extensive ramification in the inner plexiform layer. 5. The outer plexiform layer is much thinner than the inner but like it consists of a dense network of minute fibrils derived from the processes of the horizontal cells of the preceding layer and the outer processes of the rod and cone bipolar granules which ramify in it forming arborizations around the enlarged ends of the rod fibres and with the branched foot plates of the cone fibres. 6. The outer nuclear layer or layer of outer granules like the inner nuclear layer consists of several strata of oval nuclear bodies. They are of two kinds vis rod and cone granules so named on account of their being respectively connected with the rods and cones of the next layer. The rod granules are much the more numerous and are placed at different levels throughout the layer. Their nuclei present a peculiar cross-striped appearance and prolonged from either extremity of each cell is a fine process. The outer process is continuous with a single rod of the layer of rods and cones. The inner ends in the outer plexiform layer in an enlarged extremity and is embedded in the tuft into which the outer processes of the rod bipolar cells break up. In its course it presents numerous varicosities. The cone granules, fewer in number than the rod granules, are placed close to the membrana limitans externa through which they are continuous with the cones of the layer of rods and cones. They do not present any cross-striation but contain a piriform nucleus which almost completely fills the cell. From the inner extremity of the granule a thick process passes into the outer plexiform layer and there expands into a pyramidal enlargement or foot plate from which are given off numerous fine fibrils that come in contact with the outer processes of the cone bipolar. 7. The layer of rods and cones, Jacob's membrane. The elements composing this layer are of two kinds, rods and cones, the former being much more numerous than the latter except in the macular luteal. The rods are cylindrical, of nearly uniform thickness, and are arranged perpendicularly to the surface. Each rod consists of two segments, an outer and inner, of about equal lengths. The segments differ from each other as regards refraction and in their behaviour towards colouring reagents, but is coloured yellowish-brown by osmic acid. The outer segment is marked by transverse strii and tends to break up into a number of thin discs superimposed on one another. It also exhibits faint longitudinal markings. The deeper part of the inner segment is indistinctly granular, its more superficial part presents a longitudinal striation being composed of fine, bright, highly refracting fibrils. The visual purple or rhodopsin is found only in the outer segments. The cones are conical or flask shaped, their broad ends resting upon the membrane limitanz externa, the narrow pointed extremity being turned to the cooid. Like the rods each is made up of two segments, outer and inner. The outer segment is a short conical process, which, like the outer segment of the rod, exhibits transverse strii. The inner segment resembles the inner segment of the rods in structure, presenting the superficial striated and deep granular part, but differs from it in size and shape, being bulged out laterally and flask shaped. The chemical and optical characters of the two portions are identical with those of the rods. Supporting framework of the retina. The nervous layers of the retina are connected together by a supporting framework formed by the sustentacular fibres of mula. These fibres pass through all the nervous layers except flat of the rods and cones. Each begins on the inner surface of the retina by an expanded, often forked base, which sometimes contains a spheroidal body staining deeply with hematoxilin. The edges of the bases of adjoining fibres being united to form the membrana limitans in toner. As the fibres pass through the nerve fibre and ganglionic layers, they give off a few lateral branches. In the inner nuclear layer, they give off numerous lateral processes for the support of the bipolar cells, while in the outer nuclear layer they form a network around the rod and cone fibrils, and unite to form the membrana limitans external at the bases of the rods and cones. At the level of the retina nuclear layer, each sustentacular fibre contains a clear oval nucleus. Macular lutea and fovea centralis. In the macular lutea, the nerve fibres are wanting as a continuous layer. The ganglionic layer consists of several strata of cells. There are no rods, but only cones, which are longer and narrower than in other parts, and in the outer nuclear layer there are only cone granules, the processes of which are very long and arranged in curved lines. In the fovea centralis, the only parts present are one, the cones, two, the outer nuclear layer, the cone fibres of which are almost horizontal in direction, three, and exceedingly thin in a plexiform layer. The pigmented layer is thicker and it's pigment more pronounced than elsewhere. The colour of the macular seems to imbue all the layers except that of the rods and cones. It is of a richer yellow, deepest toward the centre of the macular, and does not appear to be due to pigment cells, but simply to a staining of the constituent parts. At the aura serata, the nervous layers of the retina end abruptly, and the retina is continued onward as a single layer of columnar cells covered by the pigmented layer. This double layer is known as the pals ciliares retinae, and can be traced forward from the ciliary processes onto the back of the iris, where it is termed the pals eridica retinae, or uvea. The arteria centralis retinae, and its accompanying vein, pierce the optic nerve, and enter the bulb of the eye through the porous opticus. The artery immediately bifurcates into an upper and a lower branch, and each of these again divides into a medial or nasal and a lateral or temple branch, which at first run between the hyaloid membrane and the nervous layer, but they soon enter the latter and pass forward, dividing dichotomously. From these branches a minute capillary plexus is given off, which does not extend beyond the inner nuclear layer. The macular receives two small branches, superior and inferior macular arteries, from the temporal branches and small twigs directly from the central artery. These do not, however, reach as far as the fovea centralis, which has no blood vessels. The branches of the arteria centralis retinae do not anastomose with each other. In other words, they are terminal arteries. In the fetus, a small vessel, the arteria hyaloid dea, passes forward as a continuation of the arteria centralis retinae through the vitreous humour to the posterior surface of the capsule of the lens. Anatomy of the human body, part four, by Henry Gray. The refracting media. The refracting media are three, vis aqueous humour, vitreous body, crystalline lens. The aqueous humour, humour aqueous. The aqueous humour fills the anterior and posterior chambers of the eyeball. It is small in quantity, has an alkaline reaction, and consists mainly of water, less than one-fiftieth of its weight being solid matter, chiefly chloride of sodium. The vitreous body, corpus fitrium. The vitreous body forms about four-fifths of the bulb of the eye. It fills the concavity of the retina, and is hollowed in front, forming a deep concavity, the hyaloid fossa, for the reception of the lens. It is transparent of the consistency of thin jelly, and is composed of an albumous fluid enclosed in a delicate transparent membrane, the hyaloid membrane. It has been supposed by Hanover that from its surface, numerous thin lamellae are prolonged inward in a radiating matter, forming spaces in which the fluid is contained. In the adult, these lamellae cannot be detected even after careful microscopic examinations in the fresh state. But in preparations hardened in weak chromic acid, it is possible to make out a distinct lamellation at the periphery of the body. In the centre of the vitreous body, running from the entrance of the optic nerve to the posterior surface of the lens, is a canal, the hyaloid canal, filled with lymph and lined by a prolongation of the hyaloid membrane. This canal, in the embryonic vitreous body, conveyed the arterial hyaloid from the central artery of the retina to the back of the lens. The fluid from the vitreous body is nearly pure water. It contains, however, some salts and a little albumin. The hyaloid membrane envelops the vitreous body. The portion in front of the auris serata is thickened by accession of radial fibres, and is termed the zonula ciliaris, zonul of zinc. Here it presents a series of ragly arranged furrows, in which the ciliary processes are accommodated and to which they adhere, as is shown by the fact that when they are removed, some of their pigment remains attached to the zonula. The zonula ciliaris splits into two layers, one of which is thin and lines the hyaloid fossa. The other is named the suspensory ligament of the lens. It is thicker and passes over the ciliary body to be attached to the capsule of the lens a short distance in front of its equator. Scattered and delicate fibres are also attached to the region of the equator itself. This ligament retains the lens in position, and is relaxed by the contraction of the meridional fibres of the ciliaris muscle, so that the lens is allowed to become more convex. Behind the suspensory ligament there is a saculated canal, the spatiozonalaris canal of petite, which encircles the equator of the lens. It can be easily inflated through a fine blowpipe inserted under the suspensory ligament. No blood vessels penetrate the vitreous body, so that its nutrition must be carried on by vessels of the retina and the ciliary processes, situated upon its exterior. The crystalline lens, lens crystallina, the crystalline lens enclosed in its capsule is situated immediately behind the iris, in front of the vitreous body, and encircled by the ciliary processes, which slightly overlap its margin. The capsule of the lens, capsular lentus, is a transparent, structuralist membrane, which closely surrounds the lens and is thicker in front than behind. It is brittle but highly elastic, and when ruptured the edges roll up with the outer surface in the most. It rests behind in the hyaloid fossa in the four part of the vitreous body. In front, it is in contact with the free border of the iris, but recedes from it at the circumference, thus forming the posterior chamber of the eye. It is retained in its position chiefly by the suspensory ligament of the lens, already described. The lens is a transparent, biconvex body, the convexity of its anterior being less than that of its posterior surface. The central points of these surfaces are termed repetitively the anterior and posterior poles. A line connecting the poles constitutes the axis of the lens, while the marginal circumference is termed the equator. Structure, the lens is made up of soft cortical substance and a firm central part, the nucleus. Fate lines, radiolentus, radiate from the poles to the equator, In the adult there may be six or more of these lines, but in the fetus they are only three in number and diverge from each other at angles of 120 degrees. On the anterior surface, one line ascends vertically, and the other two diverge downward. On the posterior surface, one radius ascends vertically, and the other two diverge upwards. They correspond with the free edges of an equal number of the two lines. They correspond with the free edges of an equal number of sceptre composed of an amorphous substance, which dip into the substance of the lens. When the lens has been hardened, it is seen to consist of a series of concentrically arranged laminae, each of which is interrupted at the sceptre referred to. Each lamina is built up of a number of hexagonal ribbon-like lens fibres, the edges of which are more or less serrated, the serrations fitting between those of neighbouring fibres, while the ends of the fibres come into opposition at the sceptre. The fibres run in a curved manner from the sceptre on the anterior surface to those on the posterior surface. No fibres pass from pole to pole. They are arranged in such a way that those which begin near the pole on one surface of the lens end near the peripheral extremity of the plane on the other and vice versa. The fibres of the outer layers of the lens are nucleated and together form a nuclear layer most distinct towards the equator. The anterior surface of the lens is covered by a layer of transparent columnar nucleated epithelium. At the equator the cells become elongated and their gradual transition into lens fibres can be traced. In the fetus the lens is nearly spherical and has a slightly reddish tint. It is soft and breaks down readily on the slightest pressure. A small branch from the arterial centralis retina runs forward, as already mentioned, through the vitreous body to the posterior part of the capsule of the lens, where its branches radiate and form a plexiform network which covers the posterior surface of the capsule and they are continuous around the margin of the capsule with the vessels of the papillary membrane and with those of the iris. In the adult the lens is colourless, transparent, firm in texture and devoid of vessels. In old age it becomes flattened on both surfaces slightly opaque of an amber tint and increased in density. Vessels and nerves. The arteries of the bulb of the eye are the long, short and anterior ciliary artery and the arterial centralis retina. They have already been described. The ciliary veins are seen on the outer surface of the coroid and are named from their arrangement the venous vorticose. They converge to four or five equidistant trunks which pierce the sclera midway between the sclerocorneal junction and the porous opticus. Another set of veins accompanies the anterior ciliary arteries. All of these veins open in the ophthalmic veins. The ciliary nerves are derived from the nasociliary nerve and from the ciliary ganglion. End of section 52. Section 53 of Graze Anatomy 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. Recording by Leanne Howlett. Anatomy of the Human Body. Part 4 by Henry Gray. Accessory organs of the eye. Part 1. 1C3. The accessory organs of the eye. Organa oculiaccessoria. The accessory organs of the eye include the ocular muscles, the fasci, the eyebrows, the eyelids, the conjunctiva, and the lacrimal apparatus. The ocular muscles, musculi oculi, the ocular muscles are the levator palpabris superioris, rectus medialis, rectus superior, rectus lateralis, rectus inferior, obliquus superior, obliquus inferior. The levator palpabris superioris is thin, flat, and triangular in shape. It arises from the undersurface of the small wing of the sphenoid, above and in front of the optic foramen from which it is separated by the origin of the rectus superior. At its origin, it is narrow and tendinous, but soon becomes broad and fleshy and ends anteriorly in a wide aponeurosis which splits into three lamellae. The superficial lamella blends with the upper part of the orbital septum and is prolonged forward above the superior tarsus to the palpable part of the orbicularis oculi and to the deep surface of the skin of the upper eyelid. The middle lamella, largely made up of non-striped muscular fibers, is inserted into the upper margin of the superior tarsus, while the deepest lamella blends with an expansion from the sheath of the rectus superior and with it is attached to the superior fornix of the conjunctiva. Wittnull has pointed out that the upper part of the sheath of the levator palpable becomes thickened in front and forms above the anterior part of the muscle, a transverse ligamentus band which is attached to the sides of the orbital cavity. On the medial side it is mainly fixed to the pulley of the obliquus superior, but some fibers are attached to the bone behind the pulley and a slip passes forward and bridges over the supraorbital notch. On the lateral side it is fixed to the capsule of a lacrimal gland and to the frontal bone. In front of the transverse ligamentus band the sheath is continued over the aponeurosis of the levator palpable as a thin connective tissue layer which is fixed to the upper orbital margin immediately behind the attachment of the orbital septum. When the levator palpable contracts the lateral and medial parts of the ligamentus band are stretched and check the action of the muscle. The retraction of the upper eyelid is checked also by the orbital septum coming into contact with the transverse part of the ligamentus band. The fore recti arise from a fibrous ring, annulus tendinus communus which surrounds the upper medial and lower margins of the optic foramen and encircles the optic nerve. The ring is completed by a tendinus bridge prolonged over the lower and medial part of the superior orbital fissure and attached to a tubercle on the margin of the great wing of the sphenoid bounding the fissure. Two specialized parts of this fibrous ring may be made out. A lower the ligament or tendon of zen which gives origin to the rectus inferior part of the rectus internus and the lower head of origin of the rectus lateralis and an upper which gives origin to the rectus superior the rest of the rectus medialis and the upper head of the rectus lateralis. This upper band is sometimes termed the superior tendon of lockwood. Each muscle passes forward in the position implied by its name to be inserted by a tendinus expansion into the sclera about 6 millimeters from the margin of the cornea. Between the two heads of the rectus lateralis is a narrow interval through which pass the two divisions of the oculomotor nerve, the naso ciliary nerve, the abducent nerve and the ophthalmic vein. Although these muscles present a common origin and are inserted in a similar manner into the sclera, there are certain differences to be observed in them as regards their length and breadth. The rectus medialis is the broadest, the rectus lateralis the longest, and the rectus superior the thinnest and narrowest. The obliquus oculi superior, superior oblique, is a fusiform muscle placed at the upper and medial side of the orbit. It arises immediately above the margin of the optic foramen, above and medial to the origin of the rectus superior, and passing forward ends an rounded tendon which plays in a fibrocartilaginous ring or pulley attached to the trochlear fovea of the frontal bone. The contiguous surfaces of the tendon and ring are lined by a delicate mucus sheath and enclosed in a thin fibrous investment. The tendon is reflected backward, lateral word, and downward beneath the rectus superior to the lateral part of the bulb of the eye, and is inserted into the sclera behind the equator of the eyeball, the insertion of the muscle lying between the rectus superior and rectus lateralis. The obliquus oculi inferior, inferior oblique, is a thin narrow muscle placed near the anterior margin of the floor of the orbit. It arises from the orbital surface of the maxilla lateral to the lacrimal groove. Passing lateral word, backward and upward, at first between the rectus inferior and the floor of the orbit, and then between the bulb of the eye and the rectus lateralis, it is inserted into the lateral part of the sclera between the rectus superior and rectus lateralis, near to but somewhat behind the insertion of the obliquus superior. Nerves, the levator palpabris superioris, obliquus inferior, and the recti superior, inferior and medialis, are supplied by the oculomotor nerve, the obliquus superior by the trochlear nerve, the rectus lateralis by the abducent nerve. Actions, the levator palpabris raises the upper eyelid and is a direct antagonist of the orbicularis oculi. The fore recti are attached to the bulb of the eye in such a manner that, acting singly, they will turn its corneal surface either upward, downward, medial word, or lateral word, as expressed by their names. The movement produced by the rectus superior or rectus inferior is not quite a simple one, for in as much as each passes obliquely lateral word and forward to the bulb of the eye, the elevation or depression of the cornea is accompanied by a certain deviation medial word, with a slight amount of rotation. These latter movements are corrected by the obliquus, the obliquus inferior correcting the medial deviation caused by the rectus superior and the obliquus superior that caused by the rectus inferior. The contraction of the rectus lateralis or rectus medialis, on the other hand, produces a purely horizontal movement. If any two neighboring recti of one eye act together, they carry the globe of the eye and the diagonal of these directions, these upward and medial word, upward and lateral word, downward and medial word, or downward and lateral word. Sometimes the corresponding recti of the two eyes act in unison and that other times the opposite recti act together. Thus in turning the eyes to the right, the rectus lateralis of the right eye will act in unison with the rectus medialis of the left eye, but if both eyes are directed to an object in the middle line at a short distance, the two recti medialis will act in unison. The movement of circumduction, as in looking around a room, is performed by the successive actions of the four recti. The obliqui rotate the eyeball on its antero-posterior axis, the superior directing the cornea downward and lateral word, and the inferior directing it upward and lateral word. These movements are required for the correct viewing of an object when the head is moved laterally, as from shoulder to shoulder, in order that the picture may fall in all respects on the same part of the retina of either eye. A layer of non-striped muscle, the orbitalis muscle of H. Mueller, may be seen bridging across the inferior orbital fissure. The fascia bulb, capsule of tenon, is a thin membrane which envelops the bulb of the eye from the optic nerve to the ciliary region, separating it from the orbital fat and forming a socket in which it plays. Its inner surface is smooth and is separated from the outer surface of the sclera by the periscleral lymph space. This lymph space is continuous with the subdural and subarachnoid cavities and is traversed by delicate bands of connective tissue which extend between the fascia and the sclera. The fascia is perforated behind the ciliary vessels and nerves and fuses with the sheath of the optic nerve and with the sclera around the entrance of the optic nerve. In front it blends with the ocular conjunctiva and with it is attached to the ciliary region of the eyeball. It is perforated by the tendons of the ocular muscles and is reflected backward on each as a tubular sheath. The sheath of the obliquus superior is carried as far as the fibrous pulley of that muscle. That on the obliquus inferior reaches as far as the floor of the orbit to which it gives off a slip. The sheaths on the recti are gradually lost in the perimissium but they give off important expansions. The expansion from the rectus superior blends with the tendon of the levator palpabri. That of the rectus inferior is attached to the inferior tarsus. The expansions from the sheaths of the recti lateralis and medialis are strong especially that from the lateral muscle and are attached to the lacrimal and zygomatic bones respectively. As they probably check the actions of these two recti they have been named the medial and lateral check ligaments. Lockwood has described a thickening of the lower part of the fascia bulbi which he has named the suspensory ligament of the eye. It is slung like a hammock below the eyeball being expanded in the center and narrow at its extremities which are attached to the zygomatic and lacrimal bones respectively. The orbital fascia forms the periosteum of the orbit. It is loosely connected to the bones and can be readily separated from them. Behind it is united with the dura mater by processes which pass through the optic foramen and superior orbital fissure and with the sheath of the optic nerve. In front it is connected with the periosteum at the margin of the orbit and sends off a process which assists in forming the orbital septum. From it two processes are given off. One to enclose the lacrimal gland, the other to hold the pulley of the obliquus superior in position. The eyebrows, supracilia, are two arched immanences of entanglement which surmount the upper circumference of the orbits and support numerous short thick hairs directed obliquely on the surface. The eyebrows consist of thickened entanglement connected beneath with the orbicularis oculi, corrigator, and frontalis muscles. The eyelids, palpabri, are two thin movable folds placed in front of the eye protecting it from injury by their closure. The upper eyelid is the larger and the more movable of the two and is furnished with an elevator muscle, the levator palpabri superioris. When the eyelids are open, an elliptical space, the palpable fissure, rima palpabrarum, the angles of which correspond to the junctions of the upper and lower eyelids and are called the palpable commissures or canthi. The lateral palpable commissure, commissura palpabrarum lateralis, external canthus, is more acute than the medial and the eyelids here lie in close contact with the bulb of the eye, but the medial palpable commissure, commissura palpabrarum medialis, internal canthus, is prolonged for a short distance toward the nose and the two eyelids are separated by a triangular space, the lacus lacromalis. At the basal angles of the lacus lacromalis on the margin of each eyelid is a small conical elevation, the lacrimal papilla, the apex of which is pierced by a small orifice, the punctum lacromale, the commencement of the lacrimal duct. The eyelashes, cilia, are attached to the free edges of the eyelid. They are short, thick, curved hairs arranged in a double or triple row. Those of the upper eyelid, more numerous and longer than those of the lower, curve upward. Those of the lower eyelid, curve downward so that they do not interlace in closing the lids. Near the attachment of the eyelashes are the openings of a number of glands. The ciliary glands arranged in several rows close to the free margin of the lid. They are regarded as enlarged and modified, suteriferous glands. End of section 53, recording by Leanne Howlett. Section 54 of Gray's Anatomy, 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. Recording by Leanne Howlett. Anatomy of the Human Body, Part 4 by Henry Gray. Accessory organs of the eye, Part 2. Structure of the eyelids. The eyelids are composed of the following structures taken in their order from without inward. Integument, aureolar tissue, fibers of the obicularis oculi, tarsus, orbital septum, tarsal glands, and conjunctiva. The upper eyelid has, in addition, the aponeurosis of the levator palpabri superioris. The integument is extremely thin and continuous at the margins of the eyelids with the conjunctiva. The subcutaneous aureolar tissue is very lax and delicate, and seldom contains any fat. The palpable fibers of the obicularis oculi are thin, pale in color, and possess an involuntary action. The tarsi, tarsal plates, are two thin elongated plates of dense connective tissue about 2.5 centimeters in length. One is placed in each eyelid and contributes to its form and support. The superior tarsus, tarsus superior, superior tarsal plate, the larger is of a semi-lunar form, about 10 millimeters in breadth at the center, and gradually narrowing toward its extremities. To the anterior surface of this plate, the aponeurosis of the levator palpable superioris is attached. The inferior tarsus, tarsus inferior, inferior tarsal plate, the smaller, is thin, elliptical in form, and has a vertical diameter of about 5 millimeters. The free or ciliary margins of these plates are thick and straight. The attached or orbital margins are connected to the circumference of the orbit by the orbital septum. The lateral angles are attached to the zygomatic bone by the lateral palpable raffae. The medial angles of the two plates end at the lacus lacromelus and are attached to the frontal process of the maxilla by the medial palpable ligament. The orbital septum, septum orbital palpable ligament, is a membranous sheet attached to the edge of the orbit where it is continuous with the periosteum. In the upper eyelid, it blends by its peripheral circumference with the tendon of the levator palpable superioris and the superior tarsus, in the lower eyelid with the inferior tarsus. Immediately it is thin and becoming separated from the medial palpable ligament is fixed to the lacromel bone immediately behind the lacromel sac. The septum is perforated by the vessels and nerves which pass from the orbital cavity to the face and scalp. The eyelids are richly supplied with blood. The tarsal glands, glandular tarsalis, mybomii, mybomian glands. The tarsal glands are situated upon the inner surfaces of the eyelids between the tarsii and conjunctiva and may be distinctly seen through the latter on inverting the eyelids, presenting an appearance like parallel strings of pearls. There are about 30 in the upper eyelid and somewhat fewer in the lower. They are embedded in grooves in the inner surfaces of the tarsii and correspond in lengths with the breadth of these plates. They are consequently longer in the upper than in the lower eyelid. Their ducts open on the free margins of the lids by minute foramina. Structure. The tarsal glands are modified sebaceous glands, each consisting of a single straight tube or follicle with numerous small lateral diverticula. The tubes are supported by a basement membrane and are lined at their mouths by stratified epithelium. The deeper parts of the tubes and the lateral offshoots are lined by a layer of polyhedral cells. The conjunctiva is the mucous membrane of the eye. It lines the inner surfaces of the eyelids or palpebri and is reflected over the four part of the sclera and cornea. The palpable portion, tunica conjunctiva palpabrarum, is thick, opaque, highly vascular and covered with numerous papuli, its deeper part presenting a considerable amount of lymphoid tissue. At the margins of the lids it becomes continuous with the lining membrane of the ducts of the tarsal glands and through the lacrimal ducts with the lining membrane of the lacrimal sac and nasolacrimal duct. At the lateral angle of the upper eyelid, the ducts of the lacrimal gland open on its free surface and at the medial angle it forms a semi-lunar fold, the pleica semi-lunaris. The line of reflection of the conjunctiva from the upper eyelid onto the bulb of the eye is named the superior fornix and that from the lower lid the inferior fornix. The bulb reportion, tunica conjunctiva bulbi. Upon the sclera the conjunctiva is loosely connected to the bulb of the eye. It is thin, transparent, destitute of papuli and only slightly vascular. Upon the cornea the conjunctiva consists only of epithelium constituting the epithelium of the cornea already described. Lymphatics arise in the conjunctiva in a delicate zone around the cornea and run to the ocular conjunctiva. In and near the fornices, but more plentiful in the upper than in the lower eyelid, a number of convoluted tubular glands open on the surface of the conjunctiva. Other glands analogous to lymphoid follicles and called by Henley trochoma glands are found in the conjunctiva and according to Strohmeyer are chiefly situated near the medial palpable commissure. They were first described by Brusch in his description of Pyer's patches of the small intestine as identical structures existing in the under eyelid of the ox. The caruncula lacrimelis is a small reddish conical shaped body situated at the medial palpable commissure and filling up the leicus lacrimelis. It consists of a small island of skin containing sebaceous and suteriferous glands and is a source of the whitish secretion which constantly collects in this region. A few slender hairs are attached to its surface. Lateral to the caruncula is a slight semi-lunar fold of conjunctiva, the concavity of which is directed toward the cornea. It is called the pleica semi-lunaris. Mular found smooth muscular fibers in this fold and some of the domesticated animals that contains a thin plate of cartilage. The nerves in the conjunctiva are numerous and form rich plexuses. According to Krause they terminate in a peculiar form of tactile corpuscle which he terms terminal bulb. The lacrimal apparatus lacrimelis consists of A, the lacrimal gland which secretes the tears and its expiratory ducts which convey the fluid to the surface of the eye, B, the lacrimal ducts, the lacrimal sac and the nasal lacrimal duct by which the fluid is conveyed into the cavity of the nose. The lacrimal gland, glandular lacrimelis. The lacrimal gland is lodged in the lacrimal fossa on the medial side of the zygomatic process of the frontal bone. It is of an oval form about the size and shape of an almond and consists of two portions described as the superior and inferior lacrimal glands. The superior lacrimal gland is connected to the periosteum of the orbit by a few fibrous bands and rests upon the tendons of the recti superioris and lateralis which separate it from the bulb of the eye. The inferior lacrimal gland is separated from the superior by a fibrous septum and projects into the back part of the upper eyelid where its deep surface is related to the conjunctiva. The ducts of the glands, from 6 to 12 in number, run obliquely beneath the conjunctiva for a short distance and open along the upper and lateral half of the superior conjunctival fornix. Structures of the lacrimal gland. In structure and general appearance the lacrimal resembles the cirrus salivary glands. In the recent state the cells are so crowded with granules that their limits can hardly be defined. They contain oval nuclei and the cell protoplasm is finally fibrillated. The lacrimal ducts, ductus lacrimalis, lacrimal canals. The lacrimal ducts, one in each eyelid, commence at minute orifices termed puncta lacrimalia on the summits of the papillae lacrimalis seen on the margins of the lids at the lateral extremity of the lacus lacrimalis. The superior duct, the smaller and shorter of the two, at first ascends and then bends at an acute angle and passes medial word and downward to the lacrimal sac. The inferior duct at first descends and then runs almost horizontally to the lacrimal sac. At the angles they are dilated into ampulee, their walls are dense in structure and their mucous lining is covered by stratified squamous epithelium placed on a basement membrane. Outside the ladder is a layer of striped muscle, continuous with the lacrimal part of the orbicularis oculi. At the base of each lacrimal papilla, the muscular fibers are circularly arranged and form a kind of sphincter. The lacrimal sac, sacus lacrimalis. The lacrimal sac is the upper dilated end of the nasal lacrimal duct and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla. It is oval in form and measures from 12 to 15 millimeters in length. Its upper end is closed and rounded. Its lower is continued into the nasal lacrimal duct. Its superficial surface is covered by a fibrous expansion derived from the medial palpable ligament and its deep surface is crossed by the lacrimal part of the orbicularis oculi which is attached to the crest on the lacrimal bone. Structure. The lacrimal sac consists of a fibrous elastic coat lined internally by mucous membrane. The latter is continuous through the lacrimal ducts with the conjunctiva and through the nasal lacrimal duct with the mucous membrane of the nasal cavity. The nasal lacrimal duct. Ductis nasal lacrimalis nasal duct. The nasal lacrimal duct is a membranous canalis. The nasal lacrimal duct is a membranous canal about 18 millimeters in length which extends from the lower part of the lacrimal sac to the inferior meadis of the nose where it ends by a somewhat expanded orifice provided with an imperfect valve, the pleica lacrimalis has nary formed by a fold of the mucous membrane. It is contained in an osseous canal formed by the maxilla, the lacrimal bone, and the inferior nasal conca. It is narrower in the middle than at either end and is directed downward, backward, and a little lateral word. The mucous lining of the lacrimal sac and nasal lacrimal duct is covered with columnar epithelium which in places is ciliated. End of section 54, recording by Leanne Howlett. Section 55 of Grey's Anatomy 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. Recording by David Lawrence. Anatomy of the Human Body Part 4 by Henry Gray. One D. The Organ of Hearing. Organon, auditus, the ear. The ear, or organ of hearing, is divisible into three parts. The external ear, the middle ear, or tympanic cavity, and the internal ear, or labrith, the development of the ear. The first rudiment of the internal ear appears shortly after that of the eye in the form of a patch of thickened ectoderm, the auditory plate, over the region of the hindbrain. The auditory plate becomes depressed and converted into the auditory pit. The mouth of the pit is then closed, and thus a shut sac, the auditory vesicle, is formed. From it the epithelial lining of the membranous labrith is derived. The vesicle becomes shaped, and the neck of the flask is obliterated. From the vesicle, certain diverticula are given off which form the various parts of the membranous labrith. One from the middle part forms the ductus and sacus endolomphaticus. Another from the anterior end gradually elongates and, forming a tube coiled on itself, becomes a cochlear duct. The vestibular extremity of which is subsequently constricted to form the canalis reunions. Three others appear as disc-like imaginations on the surface of the vesicle. The central parts of the walls of the discs coalesce and disappear, while the peripheral portions persist to form the semicircular ducts. Of these, the superior is the first, and the lateral, the last, to be completed. The central part of the vesicle represents the membranous vestibule, and is subdivided by a constriction into a smaller ventral part, the saccule and the large dorsal and posterior part, the utricle. This subdivision is affected by a fold which extends deeply into the proximal part of the ductus endolomphaticus, with the result that the utricle and saccule ultimately communicate with each other by means of a Y-shaped canal. The saccule opens into the cochlear duct through the canalis reunions, and the semicircular ducts communicate with the utricle. The mesodermal tissue surrounding the various parts of the epithelial labyrinth is converted into a cartilaginous ear capsule, and this is finally ossified to form the bony labyrinth. Between the cartilaginous capsule and the epithelial structures, it's a stratum of mesodermal tissue which is differentiated into three layers. Viz, an outer, forming the periosteal lining of the bony labyrinth, an inner and direct contact with the epithelial structures, and an intermediate consisting of gelatinous tissue. By the absorption of this latter tissue, the periolomphatic spaces are developed. The modliolus and osseous spiral lamina of the cochlea are not preformed in cartilage but are ossified directly from connective tissue. The middle ear and auditory tube are developed from the first pharylingial pouch. The entodermal lining of the dorsal end of this pouch is in contact with the ectoderm of the corresponding pharylingial groove. By the extension of the mesoderm between these two layers, the tympanic membrane is formed. During the sixth or seventh month, the tympanic entrum appears as an upward and backward expansion of the tympanic cavity. With regard to the exact mode of development of the ossicles of the middle ear, there is some difference of opinion. The view generally held is that the melius is developed from the proximal end of the mandibular, mankel's cartilage. The incus in the proximal end of the mandibular arch and that the stapes is formed from the proximal end of the hyoid arch. The melius, with the exception of its anterior process, is ossified from a single center which appears near the neck of the bone. The anterior process is ossified separately in membrane and joins the main part of the bone about the sixth month of fetal life. The incus is ossified from one center which appears in the upper part of its long cruce and ultimately extends into its lenticular process. The stapes first appears as a ring, annulus stapedius, encircling a small vessel, the stapedial artery, which subsequently undergoes atrophy. It is ossified from a single center which appears in its base. The external acoustic meatus is developed from the first bronchial groove. The lower part of this groove extends inward as a funnel-shaped tube, primary meatus, from which the cartilinegis portion and a small part of the roof of the osseous portion of the meatus are developed. From the lower part of the funnel-shaped tube, an epithelial lamina extends downward and inward along the inferior wall of the primitive tympanic cavity. By the splitting of this lamina, the inner part of the meatus, secondary meatus is produced, while the inner portion of the lamina forms acutaneous stratum of the tympanic membrane. The auricular or pinna is developed by the gradual differentiation of tubercles, which appear around the margin of the first bronchial groove. The rudiment of the acoustic nerve appears about the end of the third week, as a group of ganglion cells closely applied to the cephalic edge of the auditory vesticle. Whether these cells are derived from the ectoderm adjoining the auditory vesticle, or have migrated from the wall of the neural tube, is as yet uncertain. The ganglion gradually split into two parts, the vestibular ganglion and the spiral ganglion. The peripheral branches of the vestibular ganglion pass into divisions, the part superior giving rami to the superior ampulla of the superior semicircular duct, to the lateral ampulla and to the utricle, and the part inferior giving rami to the saccule and to the posterior ampulla. The proximal fibers of the vestibular ganglion form the vestibular nerve. The proximal fibers of the spiral ganglion form the cochlear nerve. The external ear consists of the expanded portion named the auricula, or pinna, and the external acoustic meadus. The former projects from the side of the head and serves to collect the vibrations of the air by which sound is produced. The latter leads inward to the external ear. The external ear consists of the expanded portion named the auricula, or pinna, and the external acoustic meadus. The latter leads inward from the bottom of the auricula and conducts the vibrations to the tympanic cavity. The auricula, or pinna, is of an ovoid form, with its larger end directed upward. Its lateral surface is irregularly concave, directed slightly forward and presents numerous eminences and depressions to which names have been assigned. The prominent rim of the auricula is called the helix. Where the helix turned downward behind a small tubercle, the auricular tubercle of Darwin is frequently seen. This tubercle is very evident about the sixth month of fetal life when the whole auricula has a close resemblance to that of some of the adult monkeys. Another curved prominence parallel with and in front of the helix is called the antihelix. This divides above into crura, between which is a triangular depression, the fossa triangularis. The narrow curved depression between the helix and the antihelix is called the scafa. The antihelix describes a curve around a deep capaceous cavity, the conca, which is partially divided into two parts by the cruise or commencement of the helix. The upper part is termed the simpa conchi, the lower part, the cavum conchi. In front of the conca and projecting backward over the myatus is a small pointed eminence, the tragus. So called from its being generally covered on its under surface with a tuft of hair resembling a goat's beard. Opposite the tragus and separated from it by the intertragic notch is a small tubercle, the antitragus. Below this is the lobule, composed of tough, ariliar and adipose tissues and wanting the firmness and elasticity of the rest of the auricula. The cranial surface of the auricula presents elevations which correspond to the depressions on its lateral surface and after which they are named. Example eminence conchi, eminence triangularis, etc. Structure. The auricula is composed of a thin plate of yellow fibrocardilage covered with integument and connected to the surrounding parts by ligaments and muscles and to the commencement of the external acoustic myatus by fibrous tissue. The skin is thin, closely adherent to the cartilage and covered with fine hairs furnished with sebaceous glands most numerous in the concha and scaphoid fossa. On the tragus and antitragus the hairs are strong and numerous. The skin of the auricula is continuous with that lining the external acoustic myatus. The cartilage of the auricula, cartilago auriculae, cartilage of the pina consists of a single piece. It gives form to this part of the ear and upon its surface are found the eminences and depressions above described. It is absent from the lobule. It is deficient also between the tragus and beginning of the helix the gap being filled up by dense fibrous tissue. At the front part of the auricula where the helix bends upward is a small projection of cartilage called the spina helicus. While in the lower part of the helix the cartilage is prolonged downward as a tail-like process, the coda helicus. This is separated from the antihelix by a fissure the fissura antitrago helicina. The cranial aspect of the cartilage exhibits a transverse furrow the sulcus antihelicus transversus which corresponds with the inferior cruise of the antihelix and separates the eminence conchi from the eminence triangularis. The eminence conchi is crossed by a vertical ridge, ponticulus, which gives attachment to the auricularis posterior muscle. In the cartilage of the auricula are two fissures, one behind the cruise helicus and another in the tragus. The ligaments of the auricula, ligamenti auricularia, valsalva ligaments of the pina, consists of two sets. One, extrinsic, connecting it to the side of the head and two, intrinsic, connecting various parts of its cartilage together. The extrinsic ligaments are two in number anterior and posterior. The anterior ligament extends from the tragus and spina helicus to the root of the zygomatic process of the temporal bone. The posterior ligament passes from the posterior surface of the concha to the outer surface of the mastoid process. The chief intrinsic ligaments are, a, a strong fibrous band stretching from the tragus to the commencement of the helix, completing the myatus in front and partly encircling the boundary of the concha, and b, a band between the antihelix and the cauda helicus. Other or less important bands are found on the cranial surface of the pina. The muscles of the auricula consist of two sets. One, the extrinsic, which connected with the skull and scalp and move the auricula as a whole. And two, the intrinsic, which extend from one part of the auricle to another. The extrinsic muscles are the auricularis anterior, superior, and posterior. The auricularis anterior, atrahens aurum, the smallest of the three, is thin, and fan-shaped, and its fibers are pale and indistinct. It arises from the lateral edge of the gallia aponeurotica, and its fibers converge to be inserted into a projection on the front of the helix. The auricularis superior, atrahens aurum, the largest of the three, is thin and fan-shaped. Its fibers arise from the gallia aponeurotica and converge to be inserted by a thin, flattened tendon into the upper part of the cranial surface of the auricula. The auricularis posterior, atrahens aurum, consists of two or three fleshy fasciculi, which arise from the mastoid portion of the temporal bone by short aponeurotic fibers. They are inserted into the lower part of the cranial surface of the conca. In man, these muscles possess very little action. The auricularis anterior draws the auricula forward and upward. The auricularis superior slightly raises it, and the auricularis posterior draws it backward. The intrinsic muscles are the helicus major, helicus minor, traegicus, antitraegicus, transversus auriculi, oblicus auriculi. The helicus major is a narrow vertical band situated upon the anterior margin of the helix. It arises below from the spina helicus and is inserted into the anterior border of the helix just where it is about to curve backward. The helicus minor is an oblique fasciculus covering the cruise helicus. The traegicus is a short, flattened vertical band on the lateral surface of the traegus. The antitraegicus arises from the outer part of the antitraegicus and is inserted into the cauda helicus and antihelix. The transversus auriculi is placed on the cranial surface of the pina. It consists of scattered fibers, partly tendinous and partly muscular, extending from the emanentia conchi to the prominence corresponding with the scapha. The oblicus auriculi, also on the cranial surface, consists of a few fibers extending from the upper and back part of the concha to the convexity immediately above it. Nerves. The auricularis anterior and superior and the intrinsic muscles on the lateral surface are supplied by the temporal branch of the facial nerve. The auricularis posterior and the intrinsic muscles on the cranial surface by the posterior auricular branch of the same nerve. The arteries of the auricula are the posterior auricular from the external carotid, the anterior auricular from the superficial temporal, and a branch from the occipital artery. The veins accompany the corresponding arteries. The sensory nerves are the great auricular from the cervical plexus, the auricular branch of the vagus, the auriculotemporal branch of the mandibular nerve, and the lesser occipital from the cervical plexus. The external acoustic meatus, meatus acousticus externus, external auditory canal or meatus, extends from the bottom of the concha to the tympanic membrane. It is about four centimeters in length if measured from the tragus. From the bottom of the concha, its length is about 2.5 centimeters. It forms an S-shaped curve and is directed at first inward, forward, and slightly upward, pars externa. It then passes inward and backward, pars media, and lastly is carried inward, forward, and slightly downward, pars interna. It is an oval cylindrical canal, the greatest diameter being directed downward and backward at the external orifice, but nearly horizontally at the inner end. It presents two constrictions, one near the inner end of the cartilaginous portion and another, the ithsmus, in the osseous portion, about two centimeters from the bottom of the concha. The tympanic membrane which closes the inner end of the meatus is obliquely directed. In consequence of this, the floor and anterior wall of the meatus are longer than the roof and posterior wall. The external acoustic meatus is formed partly by cartilage and membrane and partly by bone and is lined by skin. The cartilaginous portion, meatus, acousticus, externa, cartilaginous is about two centimeters in length. It is continuous with the cartilage of the auricula and firmly attached to the circumference of the auditory process of the temporal bone. The cartilage is deficient at the upper and back part of the meatus, its place being supplied by fibrous membrane. Two or three deep fissures are present in the anterior part of the cartilage. The osseous portion, meatus, acousticus, externa, osseous is about 16 millimeters in length and is narrower than the cartilaginous portion. It is directed inward and a little forward, forming in its course a slight curve, the convexity of which is upward and backward. Its inner end is smaller than the outer and sloped, the anterior wall projecting beyond the posterior for about four millimeters. It is marked except at its upper part by a narrow groove, the tympanic sulcus in which the circumference of the tympanic membrane is attached. Its outer end is dilated and rough in the greater part of its circumference for the attachment of the cartilage of the auricula. The front and lower parts of the osseous portion are formed by a curved plate of bone, the tympanic part of the temporal, which in the fetus exists as a separate ring, annulus tympanicus, incomplete at its upper part. The skin lining the meatus is very thin, adheres closely to the cartilaginous and osseous portions of the tube and covers the outer surface of the tympanic membrane. After maceration, the thin pouch of epidermis, when withdrawn, preserves the form of the meatus. The thick, subcutaneous tissue of the cartilaginous part of the meatus are numerous seruminous glands, which secrete the earwax, their structure resembles that of the suteriferous glands. Relations of the meatus In front of the osseous part is the condyle of the mandible, which, however, is frequently separated from the cartilaginous part by a portion of the parotid gland. The movements of the jaw influence to some extent the lumen of this latter portion. Behind the osseous part are the mastoid air cells separated from the meatus by a thin layer of bone. The arteries supplying the meatus are branches from the posterior auricular, internal maxillary, and temporal. The nerves are chiefly derived from the auricular temporal branch of the mandibular nerve and the auricular branch of the vagus. End of Section 56 Recording by Veronica Jenkins, Ottawa, Illinois 1D.2 The middle ear, or tympanic cavity The middle ear, or tympanic cavity is an irregular, laterally compressed space within the temporal bone. It is filled with air which is conveyed to it from the nasal part of the pharynx through the auditory tube. It contains a chain of movable bones which connect lateral to its medial wall and serve to convey the vibrations communicated to the tympanic membrane across the cavity to the internal ear. The tympanic cavity consists of two parts, the tympanic cavity proper, opposite the tympanic membrane, and the attic, or epitympanic recess, above the level of the membrane. The latter contains the upper half of the malleus and the greater part of the incus. Including the attic, the vertical and entroposterior diameters of the cavity are each about 15 mm. The transverse diameter measures about 6 mm above and 4 mm below. Opposite the centre of the tympanic membrane it is only about 2 mm. The tympanic cavity is bounded laterally by the tympanic membrane immediately by the lateral wall of the internal ear. It communicates behind with the tympanic entrum and through it with the mastoid air cells and in front with the auditory tube. The tegmental wall or roof, paryas tegmentalis, is formed by a thin plate of bone, the tegment tympani, which separates the cranial and tympanic cavities. It is situated on the interior surface of the petrus portion of the temporal bone close to its angle of junction with its squama temporalis. It is prolonged backward so as to roof in the tympanic entrum and forward to cover in the semi-canal for the tensor tympani muscle. Its lateral edge corresponds with the remains of the petrus squamous suture. The jugular wall or floor, paryas jugularis is narrow and consists of a thin plate of bone fundus tympani, which separates the tympanic cavity from the jugular fossa. It presents near the labyrinthic wall a small aperture for the passage of the tympanic branch of the glossovirincial nerve. The membranous or lateral wall, paryas membranesia, outer wall is formed mainly by the tympanic membrane partly by the ring of bone into which this membrane is inserted. This ring of bone is incomplete at its upper part forming a notch, notch of rivenus, close to which are three small apertures, the aiter cordi posterioris the petro tympanic fissure and the aiter cordi anterioris. The aiter cordi posterioris apertura tympanica canaliculi cordi is situated in the angle of junction between the mastoid and membranous wall of the tympanic cavity immediately behind the tympanic membrane and on a level with the upper end of the manubrium of the mullius. It leads into a minute canal which descends in front of the canal for the facial nerve and ends in that canal near the stylo mastoid foramen. Through it the cordi tympani nerve enters the tympanic cavity. The petro tympanic fissure opens just above and in front of the ring of bone into which the tympanic membrane is inserted. In this situation it is a mere slit about two millimeters in length. It lodges the anterior process and anterior ligament of the mullius and gives passage to the anterior tympanic branch of the internal maxillary artery. The aiter cordi anterioris canal of hugye is placed at the medial end of the petro tympanic fissure. Through it the cordi tympani nerve leaves the tympanic cavity. The tympanic membrane, membrana tympani, separates the tympanic cavity from the bottom of the external acoustic meatus. It is a thin, semi-transparent membrane nearly oval in form, somewhat broader above than below and is directed very obliquely downward and inward so as to form an angle of about 55 degrees with a floor of the meatus. Its longest diameter is downward and forward and measures from 9 to 10 millimeters. Its shortest diameter measures from 8 to 9 millimeters. The greater part of its circumference is thickened and forms a fibrocartilaginous ring which is fixed in the tympanic sulcus at the inner end of the meatus. This sulcus is deficient superiorly at the notch of rivenus and from the ends of this notch two bands the anterior and posterior malleolar folds are prolonged to the lateral process of the malleus. The small, somewhat triangular part of the membrane situated above these folds is lax and thin and is named the pars flakidae. In it a small orifice is sometimes seen. The manubrium of the malleus is firmly attached to the medial surface of the membrane as far as its center which it draws toward the tympanic cavity. The lateral surface of the membrane is thus concave and the most depressed part of this concavity is named the umbo structure. The tympanic membrane is composed of three strata, a lateral, cutaneous, an intermediate, fibrous and a medial, mucus. The cutaneous stratum is derived from the integument lining the meatus. The fibrous stratum consists of two layers, a radiate stratum, the fibers of which diverge in the manubrium of the malleus, and a circular stratum, the fibers of which are plentiful around the circumference but spares and scattered near the center of the membrane. Branded or geometric fibers as pointed out by Gruber are also present, especially in the posterior half of the membrane. Vessels and nerves. The arteries of the tympanic membrane are derived from the deep oricular branch of the internal maxillary which ramifies beneath the cutaneous stratum and from the stylomastered branch of the posterior oricular and tympanic branch of the internal maxillary which are distributed on the mucous surface. The superficial veins open into the external jugular. Those on the deep surface drain partly into the transverse sinus and veins of the gerometer and partly into a plexus on the auditory tube. The membrane receives its chief nerve supply from the oricular temporal branch of the mandibular, the oricular branch of the vagus and the tympanic branch of the glossopharyngeal light. The labyrinthic or medial wall peris labyrinthica inner wall is vertical in direction and presents for examination the fenestria vestibuli and cochlea, the promontory and the prominence of the facial canal. The fenestra vestibuli, fenestra ovalis is a renaform opening leading from the tympanic cavity into the vestibule of the internal ear. Its long diameter is horizontal and its convex border is upward. In the recent state it is occupied by the base of the stapus, the circumference of which is fixed by the annual ligament to the margin of the furamen. The fenestra cochlea fenestra rotunda is situated below and a little behind the fenestra vestibuli from which it is separated by a rounded elevation, the promontory. It is placed at the bottom of a funnel shaped depression and in the meserated bone leads into the cochlea of the internal ear. In the fresh state it is closed by a membrane, the secondary tympanic membrane, which is concave towards the tympanic cavity, convex towards the cochlea. This membrane consists of three layers, an external or mucous derived from the mucous lining of the tympanic cavity, an internal from the lining of the membrane of the cochlea, and an intermediate or fibrous layer. The promontory, is a rounded hollow prominence formed by the projection outward of the first tone of the cochlea. It is placed between the fenestry and it is furrowed on its surface by small grooves for the lodgement of branches of the tympanic plexus. A minute spicule of bone frequently connects the pyramidal eminence. The prominence of the facial canal, prominencia canales facialis, prominence of aqueduct of fallopius indicates the position of the bony canal in which the facial nerve is contained. This canal traverses the labyrinthic wall of the tympanic cavity above the fenestra vestibuli and behind that opening curves nearly vertically downward along the mastoid wall. The mastoid or posterior wall perius mastoidia is wider above than below and presents for examination the entrance to the tympanic entrem, the pyramidal eminence and the fossa incudis. The entrance to the entrem is a large irregular aperture which leads backward from the epitympanic recess into a considerable airspace named the tympanic or mastoid entrem. The entrem communicates behind and below with the mastoid aircells which vary considerably in number, size and form. The entrem and mastoid aircells are lined by mucus membrane, continues with that lining the tympanic cavity. On the medial wall the entrance to the entrem is a rounded eminence situated above and behind the prominence of the facial canal. It corresponds with the position of the ampulated ends of the superior and lateral semicircular canals. The pyramidal eminence is situated immediately behind the fenestra vestibuli and in front of the vertical portion of the facial canal. It is hollow and contains the stapedius muscle. Its summit projects forward toward the fenestra vestibuli and is pierced by a small aperture which transits the tendon of the muscle. The cavity in the pyramidal eminence is prolonged downward and backward in front of the facial canal and communicates with it by a minute aperture which transmits a twig from the facial nerve to the stapedius muscle. The fossa incudis is a small depression in the lower and back part of the epitympanic recess. It lodges the short crust of the incus. The carotid or anterior wall, perius carotica is wider above than below. It corresponds with the carotid canal from which it is separated by a thin plate of bone perforated by the tympanic branch of the internal carotid artery and by the deep patrosal nerve which connects the sympathetic plexus on the internal carotid artery with the tympanic plexus on the promontory. At the upper part of the anterior wall are the orifice of the semicanel for the tensor tympani muscle and the tympanic orifice of the oratory tube separated from each other by a thin horizontal plate of bone the septum canalis muscular tuberae. These canals run from the tympanic cavity forward and downward to the retiring angle between the squama and the petrus portion of the temporal bone. The semicanel for the tensor tympani. Semicanelis m tensoris tympani is the superior and the smaller of the two. It is cylindrical and lies beneath the tegment tympani. It extends on to the labyrinthic wall of the tympanic cavity and ends immediately above the finaster vestibuli. The septum canalis muscular tuberae processes cochleariformis, passes backward below this semicanel forming its lateral wall and floor. It expands above the anterior end of the finaster vestibuli and terminates there by curving laterally so as to form a pulley over which the tendon of the muscle passes. The oratory tube, tuber auditiva eustegian tube is a channel through which the tympanic cavity communicates with the nasal part of the pharynx. Its length is about 36 millimeters and its direction is downward forward and medial width, forming an angle of about 45 degrees with a sagittal plane and one from 30 to 40 degrees with a horizontal plane. It is formed partly of bone, partly of cartilage and fibrous tissue. The oscious portion pars osciotubi auditivi is about 12 millimeters in length. It begins in the carotid wall of the tympanic cavity below the septum canalis muscular tuberae and gradually narrowing ends at the angle of junction of the squama and the petrus portion of the temporal bone. Its extremity presenting a jagged margin which serves for the attachment of the cartilaginous portion. The cartilaginous portion pars cartilaginia tubi auditivi about 24 millimeters in length is formed of a triangular plate of elastic fiber cartilage, the apex of which is attached to the margin of the medial end of the oscious portion of the tube while its base lies directly under the mucous membrane of the nasal part of the pharynx where it forms an elevation that torus tuberius or cushion behind the pharyngeal orifice of the tube. The upper edge of the cartilage is curled upon itself being bent laterally so as to present on transverse section the appearance of a hook. A groove or furrow is less produced which is open below and laterally and this part of the canal is completed by a fibrous membrane. The cartilage lies in a groove between the petrus part of the temporal and the great wing of the swenite. This groove ends opposite the middle of the medial pterygoid plate. The cartilaginous and bony portions of the tube are not in the same plane, the former inclining downward a little more than the latter. The diameter of the tube is not uniform throughout being greatest at the pharyngeal orifice, least at the junction of the bony and cartilaginous portions and again increased towards the tympanic cavity. The narrowest part of the tube is termed the isthmus. The position and relation to the pharyngeal orifice are described with the nasal part of the pharynge. The mucous membrane of the tube is continuous in front with that of the nasal part of the pharynx and behind with that of the tympanic cavity. It is covered with ciliated epithelium and is thin in the osseous portion. While in the cartilaginous portion it contains many mucous glands and near the pharyngeal orifice a considerable amount of adenoid tissue which has been named by Gerlach the tube tonsil. The tube is opened during depletition by the salpinge of pharyngeus and dilatator tube. The letter arises from the hook of the cartilage and from the membranes part of the tube and blends below with the tensor of villi palatini. End of section 57. Section 58 of Grey's Anatomy 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. The tympanic cavity contains a chain of three movable ossicles, the malleus, incus, and stapes. The first is attached to the tympanic membrane, the last to the circumference of the finestra vestibuli, the incus being placed between and connected to both by delicate articulations. The malleus, so named from its fancied resemblance to a hammer, consists of a head, neck, and three processes. These are the manubrium, the anterior, and lateral processes. The head, capitulum mallei, is the large upper extremity of the bone. It is oval in shape and articulates posteriorly with the incus being free in the rest of its extent. The facet for articulation with the incus is constricted near the middle and consists of an upper, larger, and lower smaller part which form nearly a right angle with each other. Opposite the constriction, the lower margin of the facet projects in the form of a process, the cog tooth or spur of the malleus. The neck, column mallei, is the narrow contracted part just beneath the head. Below it is a prominence to which the various processes are attached. The manubrium mallei, handle, is connected by its lateral margin with the tympanic membrane. It is directed downward, medial word, and backward. It decreases in size toward its free end, which is curved slightly forward and flattened transversely. On its medial side, near its upper end, is a slight projection into which the tendon of the tensor tympani is inserted. The anterior process, processes anterior foleyi, processes gracilis, is a delicate spicule which springs from the eminence below the neck and is directed forward to the petrotympanic fissure, to which it is connected by ligamentous fibers. In the fetus, this is the longest process of the malleus and is in direct continuity with the cartilage of mechal. The lateral process, processes lateralis, processes brevis, is a slight conical projection which springs from the root of the manubrium. It is directed laterally and is attached to the upper part of the tympanic membrane and, by means of the anterior and posterior malleolar folds, to the extremities of the notch of rivenus. The incus has received its name from its supposed resemblance to an anvil, but it is more like a premolar tooth with two roots which differ in length and are widely separated from each other. It consists of a body and two crura. The body, corpus incutus, is somewhat cubical but compressed transversely. On its anterior surface is a deeply concavo convex facet which articulates with the head of the malleus. The two crura diverge from one another nearly at right angles. The short crus, crus breve short process, somewhat conical in shape, projects almost horizontally backward and is attached to the facet incutus in the lower and back part of the epitmpanic recess. The long crus, crus longum, long process, descends nearly vertically behind and parallel to the manubrium of the malleus and bending medial word ends in a rounded projection the lenticular process which is tipped with cartilage and articulates with the head of the stapes. The stapes so called from its resemblance to a stirrup, consists of a head, neck, two crura, and a base. The head, capitulum stapedus, presents a depression which is covered by cartilage and articulates with the lenticular process of the incus. The neck, the constricted part of the bone succeeding the head, gives insertion to the tendon of the stapedius muscle. The two crura, crus anteriorus and crus posteriorus diverge from the neck and are connected at their ends by a flattened oval plate, the base, basis stapedus, which forms the foot plate of the stirrup and is fixed to the margin of the finestra vestibuli by a ring of ligamentus fibers. Of the two crura, the anterior is shorter and less curved than the posterior. Articulations of the auditory ossicles Articulatiani's acicularum auditus. The incidomaleolar joint is a saddle-shaped diarthrosis. It is surrounded by an articular capsule and the joint cavity is incompletely divided into two by a wedge-shaped articular disc or meniscus. The incidostipedial joint is an inarthrosis surrounded by an articular capsule. Some observers have described an articular disc or meniscus in this joint. Others regard the joint as a syndesmosis. Ligaments of the ossicles ligamenta articularum auditus. The ossicles are connected with the walls of the tympanic cavity by ligaments three for the malleus and one each for the incus and stapes. The anterior ligament of the malleus ligamentum mallei anteriorus is attached by one end to the neck of the malleus just above the anterior process and by the other to the anterior wall of the tympanic cavity close to the petrotympanic fissure. Some of its fibers being prolonged through the fissure to reach the spinal angularis of the sphenoid. The superior ligament of the malleus ligamentum mallei superioris is a delicate round bundle which descends from the roof of the epitempanic recess to the head of the malleus. The lateral ligament of the malleus ligamentum mallei laterali external ligament of the malleus is a triangular band passing from the posterior part of the notch of vivinus to the head of the malleus. Helmholtz described the anterior ligament and the posterior part of the lateral ligament as forming together the axis ligament around which the malleus rotates. The posterior ligament of the incus ligamentum incutus posterioris is a short thick band connecting the end of the short axis of the incus to the fossa incutus. A superior ligament of the incus ligamentum incutus superioris has been described, but it is little more than a fold of mucous membrane. The vestibular surface and the circumference of the base of the stapes are covered with hyaline cartilage. That encircling the base is attached to the margin of the finestra vestibuli by a fibrous ring, the annular ligament of the base of the stapes, ligamentum annulari baseos stapedis. The muscles of the tympanic cavity musculi acicularum auditus are the tensor tympani and stapedius. The tensor tympani the larger is contained in the bony canal above the osseous portion of the auditory tube from which it is separated by the septum canalis musculotubariii. It arises from the cartilaginous portion of the auditory tube and the adjoining part of the great wing of the sphenoid as well as from the osseous canal in which it is contained. Passing backward through the canal it ends in a slender tendon which enters the tympanic cavity, makes a sharp bend around the extremity of the septum and is inserted into the manubrium of the malleus near its root. It is supplied by a branch of the mandibular nerve through the odic ganglion. The stapedius arises from the wall of a conical cavity in the interior of the pyramidal eminence. Its tendon emerges from the orifice at the apex of the eminence and passing forward is inserted into the posterior surface of the neck of the stapies. It is supplied by a branch of the facial nerve. Actions. The tensor tympani draws the tympanic membrane medialward and thus increases its tension. The stapedius pulls the head of the stapies backward and thus causes the base of the bone to rotate on a vertical axis drawn through its own center. The back part of the base is pressed inward toward the vestibule while the fore part is withdrawn from it. By the action of the muscle the tension of the fluid within the internal ear is probably increased. The mucous membrane of the tympanic cavity is continuous with that of the pharynx through the auditory tube. It invests the auditory ossicles the muscles and nerves contained in the tympanic cavity forms the medial layer of the tympanic membrane and the lateral layer of the secondary tympanic membrane and is reflected into the tympanic antrum and mastoid cells which it lines throughout. It forms several vascular folds which extend from the walls of the tympanic cavity of the ossicles. Of these one descends from the root of the cavity to the head of the malleus and upper margin of the body of the incus. A second invests the stapedius muscle other folds invest the corda tympani nerve and the tensor tympani muscle. These folds separate off pouch-like cavities and give the interior of the tympanum a somewhat honeycombed appearance. One of these pouches, the pouch of prosac, is well marked and lies between the neck of the malleus and the membrane of flaccida. Two other recesses they are formed by the mucous membrane which envelops the corda tympani nerve and are situated one in front of and the other behind the manubrium of the malleus. They are named the anterior and posterior recesses of troch. In the tympanic cavity this membrane is pale, thin, slightly vascular and covered for the most part with columnar ciliated epithelium but over the pyramidal eminence ossicles and tympanic membrane it possesses a flattened non ciliated epithelium. In the tympanic antrum and mastoid cells epithelium is also non ciliated. In the osseous portion of the auditory tube the membrane is thin but in the cartilaginous portion it is very thick, highly vascular and provided with numerous mucous glands. The epithelium which lies the tube is columnar and ciliated. Arterals and nerves. The arteries are six in number. Two of them are larger than the others. These are the tympanic branch of the internal maxillary which supplies the tympanic membrane and the stylo mastoid branch of the posterior auricular which supplies the back part of the tympanic cavity and mastoid cells. The smaller arteries are the protrosal branch of the middle meningeal which enters through the hiatus of the facial canal a branch from the ascending pharyngeal and another from the artery of the pteragoid canal which accompany the auditory tube and the tympanic branch from the internal carotid given off in the carotid canal and perforating the thin anterior wall of the tympanic cavity. The veins terminate in the pteragoid plexus and the superior protrosal sinus. The nerves constitute the tympanic plexus which ramifies upon the surface of the inflammatory. The plexus is formed by 1. the tympanic branch of the glossopharyngeal 2. the carotid tympanic nerves 3. the smaller superficial protrosal nerve and 4. a branch which joins the greater superficial protrosal. The tympanic branch of the glossopharyngeal Jacobson's nerve enters the cavity by an aperture in its floor close to the labyrinthic wall and divides into branches which ramify on the promontory and enter into the formation of the tympanic plexus. The superior and inferior carotico-tympanic nerves from the carotid plexus of the sympathetic pass through the wall of the carotid canal and join the branches of the tympanic branch of the glossopharyngeal. The branch to the greater superficial protrosal passes through an opening on the labyrinthic wall in front of the finestra vestibuli. The smaller superficial protrosal nerve from the odic ganglion passes backward through a foramen in the middle fossil of the base of the skull sometimes through the foramen ovale and enters the anterior surface of the petrus part of the temporal bone through a small aperture situated lateral to the hiatus of the facial canal. It courses downward through the bone past the genicular ganglion of the facial nerve receiving a connecting filament from it and enters the tympanic cavity where it communicates with the tympanic branch of the glossopharyngeal and assists in forming the tympanic plexus. The branches of distribution of the tympanic plexus are supplied to the mucous membrane of the tympanic cavity. A branch passes to the finestra vestibuli another to the finestra cochlie and a third to the auditory tube. The smaller superficial protrosal may be looked upon as the continuation of the tympanic branch of the glossopharyngeal through the plexus to the odic ganglion. In addition to the tympanic plexus there are the nerves supplying the muscles. The tensor tympani is supplied by a branch from the mandibular through the odic ganglion and the stapedius by a branch from the facial. The corda tympani nerve crosses the tympanic cavity. It is given off from the sensory part of the facial about six millimeters before the nerve emerges from the stylo mastoid foramen. It runs from below upward and forward in a canal and enters the tympanic cavity through the intercordi posterioris and becomes invested with mucous membrane. It traverses the tympanic cavity crossing medial to the tympanic membrane and over the upper part of the manubrium of the malleus to the carotid wall where it emerges through the intercordi posterioris canal of UGA. End of section 58.