INTRODUCTION 17 



Those who are pursuing researches in the chemistry of 

 living things are more and more definitely separated from 

 those whose studies are physical. It is scarcely possible 

 to be an authority in both subdivisions. Specialization 

 constantly becomes more pronounced. For example, the 

 subject of the electric phenomena which can be observed 

 in living tissues is extensive enough by itself to engage 

 the exclusive attention of many students. 



Methods in Physiology. Something must now be said 

 of the methods which physiologists employ. Evidently 

 they must work upon living matter since their interest is 

 in the reactions which are peculiar to it. It does not 

 follow that they always make use of intact organisms for 

 the living state may often be protracted for some time 

 in portions of animals (or plants) detached from the 

 body. Thus the muscles of a frog's leg can be preserved 

 for hours after separation from the other systems and 

 will behave in much the same way as if they were still 

 united with them. This property of "survival," which 

 is so valuable to experimenters, is much more to be relied 

 on in the so-called cold-blooded than in the warm-blooded 

 animals. 



For carrying out many researches it is necessary to use 

 living animals. We must frequently mention such pro- 

 cedures in the course of this book and it will be well at 

 the outset to speak briefly of vivisection and the objec- 

 tions which are raised against it. It is not strange that 

 experiments on animals should be viewed with abhorrence 

 by those who have been influenced by the highly colored 

 accounts of scientific misdoing which are so widely cur- 

 rent. The feeling of compassion and the impulse to 

 protect all creatures from suffering are so admirable that 

 the physiologist must have a certain sympathy with his 

 most violent critic. Nevertheless he feels that the op- 

 position to his methods is due mainly to ignorance of 

 actual conditions and misapprehension of the spirit of 

 the investigator. 



A prime fact to be reckoned with is that physiologists 



