290 



PHYSIOLOGY 



CHAP. 



Engelmann's suspension method (Fig. 126) is simpler as well as more reliable. 

 The cardiograms which it records (independent of the differences in form 

 and amplitude due to modifications in loading and length of lever) always 

 exhibit marked anatricrotism, i.e. the ascending curve rises to the summit in 

 three shoulders, and falls rapidly in a single line, as shown on Fig. 127. 

 With a signal, made by a writing lever, worked with the finger, the moment 

 at which the systole and diastole of the sinus (Ss Sd), the systole and diastole 

 of the auricles (As Ad), the systole and diastole of the ventricle (Vs Vd), 

 and the systole and diastole of the bulbus arteriosus (Bs Bd) commence can 



Fio. 123. Left : Williams' tonograph for recording movements of frog's heart ; excised and 

 attached to cannula, inserted into the ventricle by the bulbus aortae (semi-schematic). A 

 reservoir of serum, s, communicates from below with the cardiac cavity by the valve v, which 

 opens in diastole and closes in systole. A second valve v', which opens in systole and closes 

 in diastole, leads the serum back to the reservoir s. The manometer is put in communication 

 with the heart by means of an arm of the second valvular apparatus, and traces on the revolv- 

 ing cylinder the lateral pressure of the fluid coming from the heart. Right : Portion of Williams' 

 apparatus substituted for the little cup that encloses the heart, when it is desired to see the 

 changes of volume during the beats. If the small chamber containing the heart is left empty, 

 and the end of the curved arm of the manometer connected with a highly sensitive Marey's 

 tambour, the apparatus is converted into a cardiac plethysmograph. 



be accurately enough determined. The result of these experiments (according 

 to Engelmann) is that, generally speaking, the movements Vs and Vd are the 

 only ones of which the commencement is clearly traced in the cardiogram. 

 The beginning of Vs coincides with the beginning of the second rapid rise, 

 and of Vd with that of the rapid descent from the summit of the curve. By 

 using the signal, however, it is possible (taking the average of a good number 

 of experiments) approximately to determine the other periods of the pulsatory 

 cycle, and to estimate their duration in hundredths of a second. (Engelmann, 

 " Observations et experiences sur le coeur suspendu," Arch. Neerlandaises. voL 

 xxvi.) 



B. Warm -Blooded Animals. The methods employed for the graphic 

 registration of oscillations of pressure and volume of the heart in situ, 

 were discussed in the chapter. Changes in form may be recorded by the 



