THE 



C Y CLOP.EDI A 



OF 



ANATOMY AND PHYSIOLOGY. 



INSTINCT. This word is often applied to 

 the mental acts of the lower animals, as if it 

 were truly applicable to the whole of these 

 acts ; but a little consideration will shew, 

 jirst, that this word, in its more approved and 

 correct acceptation, is applicable only to a 

 part of the mental operations, which may be 

 inferred from the observation of the actions and 

 habits of animals ; and secondly, that in this 

 restricted sense, the term is applicable to a 

 part of the operations of the human mind itself; 

 and that the subject of instinct cannot be tho- 

 roughly understood, unless information regard- 

 ing it is sought in the consciousness of our 

 own minds, as well as in the observation of 

 other living beings. The study of this subject 

 is therefore equally important as a part of 

 natural history, of mental philosophy, and of 

 human physiology ; and is a good illustration 

 of the necessity of this latter science being 

 based on the observation and generalization of 

 the laws and conditions of vital action through- 

 out the whole extent of the animal creation. 



It is obvious, indeed, that various mental 

 acts, of which we are conscious in ourselves, 

 may be inferred, with perfect confidence, to 

 take place throughout the whole range of the 

 animal kingdom, and even that some of them 

 must be performed with greater energy and 

 precision in some of the lower tribes than in 

 man. The different external senses attain their 

 highest perfection in different animals ; that of 

 smell, for example, probably in the predaceous 

 mammalia, that of touch in the antennae of 

 insects, and that of sight in the predaceous 

 birds ; it is not likely that any one is enjoyed 

 in its highest perfection by man ; and what 

 have been accurately distinguished from mere 



VOL. III. 



sensations as the perceptions of external things, 

 i. e. the notions as to the qualities of these, 

 which naturally present themselves to our minds 

 in consequence of sensations being felt, would 

 seem in various instances to follow the sensa- 

 tions more quickly and more surely in other 

 animals than in us ; for it is generally allowed 

 that what appear to be acquired perceptions of 

 the eye to us, i. e. the notions of the distance, 

 size, and form of visible objects, are instanta- 

 neously made known to many of the lower 

 animals the very first time that those objects 

 make impressions on their retinae; the faculty 

 of Intuition, which we must admit as part of 

 the source of our own knowledge, appears to 

 exist in greater perfection in other animals, and 

 the notions of external things which they thus 

 acquire are amply sufficient to regulate their 

 muscular motions. 



It is equally plain that many of the strictly 

 mental acts, of which our complex trains of 

 thought are composed, are habitually performed 

 by animals ; that they have a perfect recollec- 

 tion of past sensations, implying the exercise of 

 the powers of memory and of conception ; that 

 the emotions of fear, of joy, of affection, of 

 anger, even of jealousy, are as distinctly indi- 

 cated by their actions as by those of man ; that 

 under the influence of these emotions their 

 mental operations are excited or depressed, and 

 their attention fixed or distracted, and their 

 volition excited, as in our own case ; and that 

 their actions are habitually guided by a clear 

 perception, or rather, we should say, by conti- 

 nual correct applications, of a first principle 

 of belief, which is generally admitted to 

 be an ultimate fact in the constitution of the 

 human mind, and on which much stress has been 



