ANIMAL PSYCHOLOGY. 253 



of this branch of the animal kingdom. The several 

 species thus stand in fixed relations to each other, 

 and are all bound together by the common creative 

 thought which is incorporated in the diversified forms 

 of the individual representatives of each. Man, there- 

 fore, is not permitted to overlook the fact that he is a 

 constituent member of this vertebrate branch; and 

 although endowed, relatively, with the highest capa- 

 cities, and invested with the highest organization, he 

 cannot free himself from the bond by which its sev- 

 eral members are indissolubly united. 



Among the conspicuous features of this plan of 

 structure is the brain, which is enveloped in a skull, 

 and placed in immediate connection with the organs 

 of sense. The nervous system, of which the brain is 

 the centre, is universally regarded as the seat of the 

 mental principle. Since all the vertebrate animals 

 possess both the one and the other, they are all alike 

 raised to the first condition necessary for the mani- 

 festation of intelligence. In the next place, they all 

 agree in the possession of the organ of vision, located 

 in the head in immediate connection with the brain; 

 of the organs for smelling and hearing (with the ex- 

 ception perhaps of some species), similarly placed, and 

 holding similar relations to the brain. Besides these, 

 are the senses of taste and touch. These several senses, 

 operating through similar mechanisms, have but one 

 office, that of communicating impressions of external 

 objects to the brain for the information of the mental 

 principle. By their means a second condition of in- 

 telligence is secured; namely, perception. Without 

 one or more of these senses, which are the instru- 

 ments of perception, the bare continuance of animal 



