APPLICATIONS TO PHYSIOLOGY 287 



of the same figure, the ventricle is in systolic contrac- 

 tion, which is evident by the flow of blood into the 

 reservoir. Xow, at this moment the entire square of 

 cork comes into view, expelled from the depression 

 into which it had sunk when the ventricle was 

 relaxed. 



Comparative Advantages of Mechanical and Chrono- 

 photographic Registration. — To continue, these experi- 

 ments, which constitute some of the first applications 

 of chronophotography to experimental physiology, 

 give additional information concerning the functions 

 of the heart over and above that derived from ordinary 

 cardiography. In comparing the two methods, it will 

 be seen that they attain different ends. The one by 

 means of variations in a curve expresses the minutest 

 changes in blood-pressure that occur in the cardiac 

 chambers, and indirectly this reveals the smallest 

 details of cardiac function. But this method only 

 appeals to the initiated ; it requires numerous control 

 experiments so that one may fully understand the 

 meaning of the cardiogram. The other method, strictly 

 speaking, is the direct examination of the movements 

 of the heart by a more subtle eye than ours, and one 

 that is capable of grasping in a moment the sum total 

 of the changes which take place in the different 

 cavities of the heart. The information to be derived 

 from this method is self-evident. The comparison of 

 a series of consecutive images also affords an oppor- 

 tunity of observing every visible phase of the 

 phenomenon. It affords us no information, as does 

 the cardiogram, concerning the energy which primarily 

 conduces to the changes in form ; in fact, it only gives 

 an approximate idea of the sequence of the various 

 phases of movement, because its record is one of 

 intermittent indications, instead of the continuous 

 record of a curve. Nevertheless, important discoveries 



