INSTINCT OF INSECYS. 4:7] 
it has never tasted milk, the infant seeks for its mother’s 
breast, is the effect of reason. 
Instinct, then, is not the result of a plastic nature; of 
a system of machinery; of diseased bodily action; of 
models impressed on the brain; nor of organic shootings- 
out :—it is not the effect of the habitual determination 
for ages of the nervous fluid to certain organs; nor is it 
either the impulse of the Deity, or reason. Without 
pretending to give a logical definition of it, which while 
we are ignorant of the essence of reason is impossible, 
we may Call the instincts of animals those unknown faculties 
implanted in their constitution by the Creator, by which, 
independent of instruction, observation, or experience, 
and without a knowledge of the end in view, they are 
impelled to the performance of certain actions tending 
to the well-being of the individual and the preservation 
of the species: and with this description, which is in 
fact merely a confession of ignorance, we must, in the 
present state of metaphysical science, content ourselves. 
I here say nothing of that supposed connexion of the 
instinct of animals with their sensations, which has been 
introduced into many definitions of this mysterious power, 
for two reasons. In the first place, this definition merely 
sets the world upon the tortoise; for what do we know 
more than before about the nature of instinct, when we 
have called it, with Brown, a predisposition to certain 
actions when certain sensations exist, or with ‘Tucker 
have ascribed it to the operation of the senses, or to that 
internal feeling called appetite? But, secondly, this 
connexion of instinct with bodily sensation, though pro- 
bable enough in some instances, is by no means gene- 
rally evident. We may explain in this way the instincts 
