 Dear students, in this topic we shall discuss chymography. A chymograph is an instrument that graphically records changes in the mechanical activities of animal tissues. The word chymograph comes from the Latin word which means wave writer. This term is used because of the graphical records produced by this instrument. The chymograph is used in physiological experiments related to the study of skeletal muscle contractions for example, twitch and tetanus. It is also used to study the cardiac muscle activities for example, cardiac cycle. It is also used for the measurement of blood pressure and rate of respiration. A chymograph apparatus consists of a revolving drum to which a writing stylus is attached. The stylus records changes over time on a paper which is wrapped around the drum and the writing pen and stylus are made into graphs. Dear students, now we shall take an example of chymography of frog's heart which is generally carried out in physiology labs. This chymography provides us an understanding of the cardiac cycle of frog. It also gives the clues of the site of origin of heartbeat in frog and its control. It also provides us the understanding of coordination of contractions of chambers of the heart. Here we are looking at a chymograph of frog's heartbeat. We can see the different phases of the chymograph on which the contractions of sinus venous have occurred and the contractions of oracles have also been shown by a wave deflection or the deflection of ventricles have also been shown. This pattern is repeated for the heartbeats of frog's heart. Dear students, chymography also helps us to study effect of various factors on cardiac output. For example, when we want to study the effect of temperature or various ions or acetylcholine or epinephrine, we use chymography.