200 EVOLUTION AND MAN S PLACE IN NATURE 



greatly, as appears when the brain of the dog is com 

 pared with the brain of the ape. 1 Yet their functions 

 are nearly identical, excepting provision for diverse 

 sensory apparatus. The search for evidence of intelli 

 gence leads us to put out of account differences of form 

 in the central organ, and to deal largely with interpre 

 tation of signs, quite apart from specialties in outward 

 forms of action. Here, signs of intelligence in the 

 dog prove even more impressive, because of the fact 

 that the bodily structure of the animal renders imita 

 tion of the forms of human action almost impossible. 

 Some considerable allowance must be made for this, 

 if we are to be exact in our conclusions. On the other 

 hand, when comparison here seems greatly to the dis 

 advantage of the monkey and ape, full value must be 

 assigned to the long period of the dog s companion 

 ship with man, which has left a deep imprint on 

 the species. 



Human agency and animal co-operation are now to 

 be considered in their possible relations to each other, 

 mainly for the purpose of ascertaining when inter 

 change of understanding occurs, and to what extent. 

 This method of inquiry is determined by the history 

 of life on the earth, since co-operation and domestica 

 tion of animals have been settled by natural affinities. 

 The intellectual test warrants us in classifying the 

 higher mammals as we do. This appears when we 

 contrast these animals with others lower in the scale. 

 The lower the animal, the more difficult it is for us 

 to direct its activity, so as to secure co-operation in 

 our work. This is a testimony adverse to the inference 



1 I have given the illustrations in The Relations oj Mind and 

 Brain, p. 99, and p. 154. 



