. Kirkes' handbook of physiology . raph carefully and the whole record fixed in shellac. When the record is dry, count the rate of the heart-beat from the recordand measure the time of the cardiac systole and diastole, and the time ofpause at the end of the diastole. If these facts are taken from records securedunder different conditions of exercise, etc., as outlined in the preceding ex-periment, then they may be brought together in a table for convenience ofinspection. A comparison of such results will usually show that with thehigher heart-rates the decrease of the time of the cardiac cycle
. Kirkes' handbook of physiology . raph carefully and the whole record fixed in shellac. When the record is dry, count the rate of the heart-beat from the recordand measure the time of the cardiac systole and diastole, and the time ofpause at the end of the diastole. If these facts are taken from records securedunder different conditions of exercise, etc., as outlined in the preceding ex-periment, then they may be brought together in a table for convenience ofinspection. A comparison of such results will usually show that with thehigher heart-rates the decrease of the time of the cardiac cycle is at the ex-pense of the time of the diastole; in other words, the time of the systole re-mains fairly constant while the time of the diastole increases or decreaseswith the rate, a fact to which Hiirthle has drawn attention, figure 157. 3. The Rate and Sequence of the Contractions of the FrogsHeart. Destroy the brain of the frog and open the thorax, but donot destroy the pericardium. Count the rate of the heart per minute, then. Fig. an.—Heart Lever for Frog or Turtle Hearts. remove the pericardium and make a second determination after the heart isexposed to the air. The different parts of the heart when exposed are easilyidentified and the contractions which take place in definite sequence can bedetermined without difficulty. Make this determination for the ventricle,auricle, and sinus venosus by direct observation. THE CIRCULATION OF THE BLOOD Prepare a cardiac lever as shown in figure 211, taking special care to ar-range the foot so that it will not bind on the lever when in motion. Adjustthe foot of the lever on the exposed ventricle and bring its point to write onthe smoked paper of a recording cylinder. This cylinder should travel atthe rate of about 1 cm. per second and its speed be determined by the writingpoint of an electric magnet which is connected with the electric-clock circuitmarking seconds. Take care to adjust the time magnet in a vertical linewith the wri
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