136 THE SPIRIT OF THE SOIL 



excites it, whereas the injection of it into a man and 

 into most other animals serves to soothe the nerves 

 and induce sleep, will have it that the experimental 

 physiologist is following a will-o'-the-wisp when he 

 attempts to draw general conclusions from the 

 experiments he performs on the lower animals. I 

 have frequently been told that experiments con- 

 ducted on the dog, such as problems of digestion, 

 are valueless because the dog will swallow and digest 

 bones, whereas the normal man who ate his meals 

 on similar lines would suffer terribly from indigestion. 

 The main underlying fallacy vitiating the anti- 

 vivisection campaign when the opposition is not 

 due merely to sentimentalism is the common belief 

 that in cases where living tissue is concerned the 

 relation between cause and effect is less rigid than 

 it is in the case of lifeless matter. Scientific biology 

 is frankly based on the principle that causal rela- 

 tions do obtain rigidly so far as the material side of 

 life is concerned, and many biologists returning to 

 the problem of predestination and free will would 

 hold something closely akin to the doctrine of pre- 

 destination, and contend that every act is the 

 inevitable result of an intensely complex set of 

 causes. 



In tracing out causal relations in biology the 

 worker is confronted with formidable difficulties. 

 While the physicist or chemist is usually able to 

 simplify his problem by eliminating all confusing 

 issues, the biologist has present, as the basis of 

 nearly all his work, the intensely complex animal or 

 vegetable cell, or the even more complex living 



