364 FUNCTIONS OF THE NERVOUS SYSTEM. 



world in the full possession of all his powers, he would wait to eat when 

 hungry, until experience had taught him that the swallowing of food would 

 relieve the uneasy feeling. It has been already shown, that, in the infant, 

 the act of sucking may be performed even without a Cerebrum ( 386, c) ; 

 and for this and other similar actions, therefore, it is doubtful whether con- 

 sciousness is a requisite condition. Adult animals, whose Cerebral hemi- 

 spheres have been removed, will eat food that is put into their mouths, although 

 they will not go to seek it; and this is the case with many Human idiots. 

 When the functions of the Brain are disturbed, or in partial abeyance, as in 

 fever, we often see a remarkable return to the instinctive propensities in 

 regard to food; and the Physician frequently derives important guidance as 

 to the patient's diet and regimen (particularly as to the administration of 

 wine), from the inclination or disinclination which he manifests. 



479. The difference between actions of a purely Instinctive character, and 

 those which rather result from the Intellectual faculties prompted by the in- 

 stinctive propensities, is well seen in comparing Birds with Insects. Their 

 Instinctive tendencies are of nearly the same kind ; and the usual arts which 

 they 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 practised 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 is not doubted, by those who have attentively 

 observed 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 the 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 pecu- 

 liar 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 possessing 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. This is the case with most 

 Herbivorous quadrupeds, and with Rabbits, Guinea-pigs, &c. ; as well as with 

 the Gallinaceous Birds. 



480. The attachment which is formed to Man, by certain Mammalia of 

 higher orders, such as the Dog, the Horse, and the Elephant, is evidently of 

 a more elevated kind, and involves a much larger number of considerations. 

 The Intelligence of such animals is peculiarly exhibited in their Edueability ; 

 that is, in the facility with which their natural habits may be changed by 

 the new influences to which they are subjected, and the complication of the 

 mental processes which they appear to perform under their altered circum- 

 stances. Their actions are evidently the result, in many instances, of a com- 

 plex train of reasoning, differing in no essential respect from that which Man 

 would perform in similar circumstances ; so that the epithet, "half reason- 

 ing," commonly applied to these animals, does not express the whole truth ; 

 for their mental processes are of the same kind with those of Man, and differ 

 more in the degree of control which the animal possesses over them, than they 

 do in their own character. We have no evidence, however, that any of the 

 lower animals have a voluntary power of guiding, restraining, or accelerating 

 their mental operations, at all similar to that which Man possesses ; these 



