6 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 modihestion 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 
tem may be so varied and formed by the 
reator as to respond in the way that he wills, 
to pulses upon them from the physical powers 
of nature.”+ 
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 
ay, aigp agents takes place; but if it be meant 
y 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 al! 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 mental effort, but 
the occurrence of that effort in every case 
when it is required must in all probability be 
always held as an ultimate fact 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 hag 
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 
* See 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= 
riaemes the instincts of animals, as we shall 
afterwards state, are of uliar importance 5 
but the inferences are She scien whatever o ‘ 
nion we may adopt as to the mode in which 
the Divine Intelligence so indicated rules the” 
wills of the animal creation. ih 
Having said so much of the yyeripenie 
of this class of phenomena, and —- 
to set them in the proper point of view, we 
shall next offer a very rapid sketch of the 
fr daa instincts exhibited in the different i 
of animals, arranging them simply ing to 
the purposes which they seem pit 
serve, and shall conclude with a few general 
reflections. bs 
It may be premised that it certainly seems 
— 
reasonable @ priori to suppose, that the strac- 
ture of the nervous system, and ially of 
the brain, of different animals, will some 
relation to the kind of instinctive 
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 cord, medulla 4 
and optic lobes (or corpora quadrigemina), in the 
higher animals, this relation may be distinetly | 
perceived; and it has been further confidently | 
stated by some phrenologists, that strong evi- — 
dence of sur of their peculiar doctrines — 
may be deduced from observation of the size 
andi form of the brains of animals, as pm 2 | 
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 continualh 
guided and ruled by the laws of instinct; , 
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 bein 
much larger in proportion to the spinal : 
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 
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 
ration of these animals, because we know that 
only part of the central masses of the nervous system 
of either, concerned in that function, is the medulla 
oblongata. 
