APPLICATIONS TO PHYSIOLOGY 281 



of the aorta, and curves round, so as to pour its 

 contents into the veinous reservoir. 



In following the chronophotographic images which 

 correspond to the successive phases of the cardiac cycle, 

 the series must be read from left to right. It will be 

 noticed at once that in the first position no blood is 

 passing into the veinous reservoir through the arterial 

 tube, the ventricle is consequently relaxed (diastole). 



The positions, 2, 3, 4, and 5, show a jet of blood 

 flowing into the reservoir, the ventricle is therefore 



FrG. 197.— Seven success ve photographs of a tortoise's heart with artificial circula- 

 tion. The series must be read from left to right. They are taken at intervals 

 of ^j of a second. In each member of the series the auricle is on the left and the 

 ventricle on the right. From the 2nd to the 5th image the ventricular systole may 

 be recognized by tiie stream ot blood which \ ours into the venous reservoir. 



contracted (systole). Finally, positions 6 and 7, 

 in which the jet of blood can no longer be seen, 

 represents a fresh diastolic period. The same phe- 

 nomena continue indefinitely, and pursue the same 

 sequence of events as already described. 



The series of positions might, therefore, be transposed, 

 with No. 1 immediately following No. 7. 



As for the heart, nothing but the contour can be 

 seen, and this indicates the alternate dilatations and 

 contractions of the auricle and ventricle. 



