308 THE MENTAL CAPACITIES AND 



mentary Thoughts, or more developed Emotions and 

 Volitions. 



The survey since taken of some of the principal forms 

 of the Brain in Quadrupeds and Quadrumana reveals a 

 very marked increase in the relative size and complexity 

 of the Cerebral Hemispheres in each of these great classes. 

 And though no distinct serial order is to be traced, it 

 must be obvious from the preceding descriptions and 

 figures, that the brain of the higher Apes presents almost 

 as great an advance in relative size and complexity over 

 that of the higher Quadrupeds, as that which characterizes 

 the brain of these latter animals in comparison with the 

 brain of Birds. 



It remains, therefore, briefly to consider the scope of 

 the mental life of Quadrupeds and Quadrumana for com- 

 parison with that of Birds. The materials for arriving at a 

 judgment upon this point must still be of the same order 

 as they were in the case of animals lower in the scale of 

 organization. We can only study their actions in the 

 records which have been given of them, striving to inter- 

 pret them in the manner previously indicated (p. 196) by 

 the reflected light derived from our knowledge of human 

 intelligence and human actions and yet not too much 

 from the mere human point of view. 



It is worth while here to take note of the fact that 

 the most intelligent Quadrupeds and more especially 

 Elephants have the advantage of bringing into play a 

 rather highly developed sense of Touch, in aid of their 

 other acute and highly discriminative senses of Sight, 

 Smell, and Hearing ; and also that the same four sen- 

 sorial endowments are commonly in active operation 

 among Quadrumana although with them Smell seems 

 to diminish in importance, while the more definite and 



