THE CONQUEST OF DISEASE 



ing the bodily functions- -instruments for test- 

 ing the pressure of the blood, the relation of 

 the intake of foods to the secretions, the char- 

 acter of the nervous reflexes, the weight of the 

 animal, the composition of the air which it ex- 

 hales, and innumerable observations of a simi- 

 lar nature which scientific accuracy demands. 

 The physiologists of the whole world freely 

 publish the results of their studies, and work in 

 cooperation, one taking up a line of research 

 where another has left off, and carrying it on. 

 Thus all of the information concerning the 

 functions of a certain structure does not ema- 

 nate from a single source but is collected from 

 observers all over the world. 



Teaching Another use made of living animals is the 



purposes. demonstration for teaching purposes of the 



functions of organs. Let us take for example 

 the heart. An animal such as a calf is anesthe- 

 tized with ether, the breast bone is removed and 

 the heart exposed. After the demonstration 

 the anesthetic is continued in an excessive 

 amount and the animal killed. It is a wonder- 

 ful sight to see the living heart in operation, 

 propelling the life-giving stream through the 

 body. Its action cannot be appreciated by 

 examining the dead heart. When the heart 



