HISTORICAL REVIEW 9 



of speculation in guiding and unifying experimental work; 

 on the other he saw the necessity of founding philosophical 

 speculation on experimental facts. This broad view re- 

 sulted in much comparative work especially in physiology 

 and psychology, work which had a direct bearing on the 

 nature of psychic processes as well as on the nature of 

 physiological activity. Miiller worked on the higher 

 animals almost exclusively. His aim was to analyze the 

 phenomena of life as he found them in these organisms. 

 His followers, Wohler, Liebig, Helmholtz, du Bois-Rey- 

 mond, Lotze, Weber, Fechner and others, perpetuated this 

 aim, but they did not retain his breadth of spirit. Some 

 confined their investigations to the chemical side of physi- 

 ology, others to the physical side, and still others to pure 

 psychology. The question as to the origin and evolution 

 of vital phenomena, especially psychic phenomena, was not 

 yet prominent, if indeed it had been at all considered. The 

 behavior of lower animals had been studied to some extent, 

 but the Cartesian doctrine that there is no resemblance 

 between the mind of man and that of animals was still very 

 generally accepted. 



5. Evolution and its Effect on the Study of Behavior of 



Plants and Animals 



With the establishment of the theory of evolution, there 

 appeared a new incentive in the study of animal behavior. 

 Darwin had demonstrated in a convincing manner the 

 structural interrelationship between various animals, in- 

 cluding man. It seemed clear that the complex anatomical 

 structures found in the higher animals had their origin 

 in the simpler structures found in the lower. Could the 

 same be said with reference to behavior? Did the mental 

 phenomena in man have their origin in the lower animals? 

 If so, then there must be some evidence of mental activity 

 in the lower animals, the psychic phenomena in these 



