INSTINCT. 



idea which other philosophers have maintained, 

 of intermediate agents between the Divine will 

 and the living beings on earth, by which the 

 actions of the latter are guided ;* but in pro- 

 secuting this idea he is disposed to regard the 

 proximate cause of instinct, as he expresses it, 

 not as metaphysical, but merely as physical, 

 and to suppose that "light, heat, and air, or 

 any modification of them " may be the inter- 

 mediate agents " employed by the Deity to 

 excite and direct animals, when their intellect 

 cannot, in their instinctive operations;" and 

 that " the organization of the brain and nervous 

 system may be so varied and formed by the 

 Creator as to respond in the way that he wills, 

 to pulses upon them from the physical powers 

 of nature."f 



On this it may be observed that this last 

 sentence expresses no more than the truth, 

 whatever opinion we may form as to the mode, 

 in which the response of the nervous system 

 of an animal to the impressions made on it by 

 physical agents takes place; but if it be meant 

 by the expression, that the proximate cause of 

 instinct is probably not metaphysical but 

 physical, to exclude all mental operation, and 

 all consciousness of effort, from the instinctive 

 actions of animals, we can regard the theory 

 only as a denial of all mental acts or affections in 

 any of the lower animals, and as easily con- 

 tradicted by the whole analogies of their struc- 

 ture, by observation of their habits, and by 

 the evidence of our own consciousness in the 

 performance of those precisely similar instinc- 

 tive actions which have been noticed above. 



It seems quite unreasonable to doubt that 

 the immediate cause of all the actions that we 

 call instinctive, is a strictly mtntnl effort, but 

 the occurrence of that effort in every case 

 when it is required must in all probability be 

 always held as an ultimate Juft in the animal 

 ceconomy ; and all speculations as to its inti- 

 mate nature or proximate cause may be re- 

 garded as mere conjectures, on a subject which 

 is beyond the reach of the human faculties. 

 Nor would any thing be gained, in the infer- 

 ence as to final causes, from establishing any one 

 of these conjectures ; for the mental constitution 

 of man himself, and of the whole lower ani- 

 mals, is equally a part of the contrivance of 

 the Divine Artificer of the world, as the laws 

 of motion or the properties of light. He who 

 could make man after his own image could 

 assuredly impart such mental propensities to 

 other beings, as well as to man, as were ne- 

 cessary for the ends for which the creation was 

 designed. And when we attempt, in all hu- 

 mility, but at the same time in confident re- 

 liance on the mental powers which He has 

 vouchsafed to us, to draw inferences as to His 

 existence and attributes from the study of 

 created things, we do so, not by vainly attempt- 

 ing to comprehend the nature of the energy by 

 which any of the changes (physical or mental) 

 occurring around us are effected, but simply by 

 observing the adaptation of means to ends in 

 those regular and uniform laws which we are 



* Sec vol. ii. p. 243-4. 

 t Vol. ii. p. 255-6. 



enabled to infer from the observation of such 

 changes, which we ascribe to His authority, 

 and beyond which we feel that it is not yet 

 given us, by any exercise of our minds, to 

 ascend. In enabling us to draw those in- 

 ferences, the instincts of animals, as we shall 

 afterwards state, are of peculiar importance ; 

 but the inferences are the same, whatever opi- 

 nion we may adopt as to the mode in which 

 the Divine Intelligence so indicated rules the 

 wills of the animal creation. 



Having said so much of the characteristics 

 of this class of phenomena, and endeavoured 

 to set them in the proper point of view, we 

 shall next offer a very rapid sketch of the 

 varied instincts exhibited in the different tribes 

 of animals, arranging them simply according to 

 the purposes which they seem destined to 

 serve, and shall conclude with a few general 

 reflections. 



It may be premised that it certainly seems 

 reasonable a priori to suppose, that the struc- 

 ture of the nervous system, and 1 especially of 

 the brain, of different animals, will bear some 

 relation to the kind of instinctive propensities 

 which they exhibit. In the size of the sen- 

 sitive and motor nerves, and portions of the 

 cerebro-spinal axis whence these originate, par- 

 ticularly the spinal tord, medulla oblongata, 

 and optic lobes (or corpora quadrigemina), in the 

 higher animals, this relation may be distinctly 

 perceived; and it has been further confidently 

 stated by some phrenologists, that strong evi- 

 dence of certain of their peculiar doctrines 

 may be deduced from observation of the size 

 and form of the brains of animals, as compared 

 with their instincts ; but this last speculation 

 certainly cannot be carried further than the 

 vertebrated animals, which form but a small 

 part of the living beings that are continually 

 guided and ruled by the laws of instinct; and 

 even in them no such relation of the size and 

 form of the brain, or of any part of the brain, to the 

 general intelligence of an animal, or to any par- 

 ticular instinct, has been fully ascertained. In- 

 deed, until some such essential difference shall 

 be observed between the habits and instincts of 

 the dolphin, or other cetaceous animals, and the 

 predaceous fishes, as may correspond to the 

 extraordinary difference of the size and struc- 

 ture of their brains, (that of the former being 

 much larger in proportion to the spinal cord 

 than the human brain, and of complex struc- 

 ture, while that of the latter is not larger than 

 the optic lobes or corpora quadrigemina of the 

 same animal, and of very simple structure,) 

 such speculations may be safely distrusted.* 



Mr. Kirby has stated that the principal in- 

 stincts of animals may be referred to three 

 heads; those relating to their food, those re- 

 lating to their propagation and the care of their 

 offspring, and those relating to their hybernation. 

 But this enumeration is certainly defective, 

 and indeed will hardly include several which 



* We cannot suppose this difference to be con- 

 nected with the difference in the mode of respi- 

 ration of these animals, because we know that the 

 only part of the central masses of the nervous system 

 of either, concerned in that function, is the medulla 

 oblonguta. 



