562 FUNCTIONS OF THE CEREBRO -SPINAL NERVOUS SYSTEM. 



that their actions, though evidently adapted to the attainment of certain 

 ends, are very far from evincing a designed adaptation on the part of the 

 beings that perform them, such as that of which we are ourselves conscious 

 in our own voluntary movements, or Which we trace in the operations of the 

 more intelligent Vertebrata. For, in the first place, these actions are inva- 

 riably performed in the same manner by all the individuals of a species, 

 when the conditions are the same; and thus are obviously to be attributed 

 rather to a uniform impulse, than to a free choice; the most remarkable 

 examples of this being furnished by the economy of Bees, Wasps, and other 

 "social" Insects, in which every individual of the community performs its 

 appropriate part, with the exactitude and method of a perfect machine. The 

 very perfection of the adaptation, again, is often of itself a sufficient evidence 

 of the unreasoning character of the beings which perform the work ; for, if 

 we attribute it to their own intelligence, we must admit that this intelligence 

 frequently equals, if it does not surpass, that of the most accomplished Hu- 

 man reasoner. 1 Moreover, these operations are performed without any guid- 

 ance from experience ; for it can be proved in many cases, that it is impos- 

 sible for the beings which execute them to have received any instruction 

 whatever ; and we see that they do not themselves make any progressive 

 attempts towards perfection, but that they accomplish their work as well 

 when they first apply themselves to it, as after any number of repetitions of 

 the same acts. It is interesting to observe, moreover, that as these instinc- 

 tive operations vary at different periods of life, so there is a corresponding 

 variation in the structure of the Nervous system. Thus we see that, in the 

 larva of the Insect, these operations are entirely directed towards the acqui- 

 sition of food ; and its organs of sense and locomotive powers are only so Un- 

 developed as to serve this purpose. But in the imago or perfect Insect, the 

 primary object is the continuance of the race; and the sensorial and motor 

 endowments are adapted to enable the individual to seek its mate, and to 

 make preparations (frequently of a most elaborate kind) for the nurture of 

 the offspring. Hence we can scarcely fail to arrive at the conclusion, that 

 the adaptiveness of the instinctive operations of Insects, etc., lies in the 

 original construction of their nervous system, which causes particular move- 

 ments to be executed in direct respondence to certain impressions and sensa- 

 tions. And this view is confirmed by the comparison of such movements 

 with those which, in the Human subject, are most directly concerned in the 

 maintenance of the life of the individual, and in the perpetuation of the 

 race. For we have the evidence of our own consciousness in regard to these, 

 that, however obvious their purpose may be, and however complete their 

 adaptation to that purpose, they are performed, not with any notion of that 

 purpose, but at the prompting of an irresistible impulse which is not only 

 independent of all intelligent appreciation of the result, but may produce its 

 effect without even affecting the consciousuese of the agent. Thus the infant 

 seeks the nipple, and puts its muscles into suctorial action, without any 

 knowledge, derived from experience, that by so doing it will relieve the 

 uneasy feeling of hunger ; and if we could imagine a man coming into the 

 world with the full possession of all his faculties, we may feel tolerably cer- 

 tain that he would not wait to eat until he had learned by experience his 

 dependence upon food. We shall see that adult animals whose Cerebral 

 hemispheres 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 destroyed, or in partial abey- 

 ance, as in fever, we often observe a remarkable return to the instinctive 



1 See Princ. of Comp. Fhys., 4th edit., p. 694. 



