THE CEREBRUM, AND ITS FUNCTIONS. 695 



part only traversed by them, as is the case with that of all the lower centres> 

 clearly mark it out as the highest in its functional relations, and as minister- 

 ing, so far as any material instrument may do, to the exercise of those psy- 

 chical powers, which, in Man, exhibit so remarkable a predominance over 

 the mere animal instincts. This conclusion is fully borne out, when we 

 extend our inquiries from Human to Comparative Anatomy ; for with some 

 apparent exceptions, which there would probably be no great difficulty in 

 explaining if we were in possession of all the requisite data, there is a very 

 close correspondence between the relative development of the Cerebrum in 

 the several tribes of Vertebrata, 1 and the degree of Intelligence they respec- 

 tively possess, using the latter term as a comprehensive expression of that 

 series of mental actions which consists in the intentional adaptation of means 

 to ends, based on definite ideas as to the nature of both. It is not always 

 easy to say, in the case of the lower animals, what parts of their actions are 

 to be attributed to automatic impulse (i. e., to be considered as Instinctive), 

 and what should be regarded as the results of Intelligence. The character 

 of Intelligent actions, however, as compared with Instinctive ( 563), is 

 usually shown (1) in the variety of means which are adopted to compass the 

 same ends, and this not merely by different individuals and by successive 

 generations, but by the same individual at different times; (2) by the im- 

 provement in the mode of accomplishing the object, which results from the 

 intelligent use of experience, and from the greater command of means 

 which is progressively attained ; and (3) by the conformity of the means to 

 altered circumstances, so that the character of adaptiveuess is still main- 

 tained, however widely the new conditions may depart from those which must 

 be considered as natural to the species. 



563. The difference between actions which proceed from the Intellectual 

 faculties prompted by the instinctive propensities, and those of a purely 

 Instinctive character, is well seen in comparing Birds with Insects. The 

 Instinctive tendencies of the two classes are nearly of the same kind ; and 

 the usual arts which both exhibit in the construction of their habitations, in 

 procuring their food, and in escaping from danger, must be regarded as 

 intuitive, on account of the uniformity with which they are practiced by 

 different individuals of the same species, and the perfection with which they 

 are exercised on the very first occasion. But in the adaptation of their 

 operations to peculiar circumstances, Birds display a variety and fertility of 

 resource, far surpassing that which is manifested by Insects ; and it can 

 scarcely be doubted by those who attentively observe their habits, that in 

 such adaptations they are often guided by real intelligence. This must be 

 the case, for example, when they make trial of several means, and select 

 that one which best answers that purpose ; or when they make an obvious 

 improvement from year to year in the comforts of their dwelling; or when 

 they are influenced in the choice of a situation by peculiar circumstances, 

 which in a state of nature can scarcely be supposed to affect them. The 

 complete domesticability of many Birds is in itself a proof of their possess- 

 ing a certain degree of intelligence; but this alone does not indicate the 

 possession of more than a very low amount of it; since many of the most 

 domesticable animals are of the humblest intellectual capacity, and seem to 

 become attached to Man, principally as the source on which they depend for 

 the supply of their animal wants. But there are certain tribes of Birds, 

 especially the Parrots and their allies, which possess an extraordinary degree 

 of educability, and which manifest a power of performing simple acts of 



1 See Princ. of Comp. Phys., \ 662 et seq. 



