288 MOVEMENT 



in the realm of physiology may be looked for from 

 chronophotography. 



Movements which, in the case of the small heart of 

 a tortoise, have only been sketched in outline, should 

 be more fully studied in the case of large-sized tortoises, 

 for the photographs would be larger and more instruc- 

 tive. Better still to operate on the heart of large 

 mammals, proceeding in the orthodox manner by 

 opening the thorax and inducing artificial respiration. 

 If the heart then be whitened as before described, and 

 a strong beam of light directed on the organ, photo- 

 graphs can be taken containing details not to be found 

 when the hearts of small animals are employed. For 

 instance, one may observe the prominence caused by 

 arteries and veins, the muscular fasciculi, the folds of 

 the serous membranes, and the displacements of the 

 heart within the cavity of the pericardium, etc. 



The effects of electrical or other excitation applied 

 to the different points of the surface of the heart can 

 be estimated with extreme precision. Graphic regis- 

 tration and chronophotography give, therefore, very 

 different kinds of information concerning the heart, 

 but both are equally useful. Just as auscultation and 

 percussion, though they greatly differ, nevertheless 

 contribute with equal efficiency towards the diagnosis 

 of the physical condition and the functional adequacy 

 of the heart. 



One could indefinitely multiply examples of the 

 various applications of this new method to experi- 

 mental physiology. We have already mentioned a 

 few in passing ; but chronophotography enables us to 

 determine the function proper to each muscle in the 

 act of locomotion, by observing the prominence caused 

 by the muscle in contracting during the various phases 

 of the movement. 



But if there is one question more obscure than 



