244 PHILOSOPHY OF ZOOLOGY. 
stance, with this modification, that soft substances are pre- 
ferred in youth. In the mammalia, the appetite is directed 
to liquids alone, the milk of the mother, in the first periods 
of existence, and, afterwards, to a mixture of solids and 
fluids. Yet this instinctive power regulates with equal 
success, in these different periods, the disimilar movements 
of sucking and chewing. 
In many animals, such as the mammalia, the nourish- 
ment of the first period of life is provided by the parents, so 
that all the exertion necessary for this instinctive power to 
make, is confined to the proper employment of the food thus 
brought within the reach of the suitable organs. But, 
with many other animals, the case is widely different. ‘They 
are brought forth in situations where there is no parent to 
assist this appetite, nor food provided for its supply. In 
such cases, this instinct must execute more complicated 
movements, and lead the individual to those places where 
food is to be obtained, and afterwards direct the choice. It 
is this influence that guides the caterpillar to the leaf,—the 
duckling to the pool, and the samlet to the ocean. 
Under the controul of this appetite, and, prior to all ex- 
perience, each species is directed to seek the kind of food 
which affords it the most suitable nourishment, and to shun 
that which would be deleterious. Thus, in looking at a pas- 
tured field, we observe that there are some plants which are 
left untouched, while others are cropped to the ground. But 
as the tastes of animals, in this respect, are exceedingly 
various, we observe that what is left untouched by one spe- 
cies, 1s greedily devoured by another. Nay, what is eaten 
by the goat, for example, with avidity, and with impunity 
by the horse or sheep, as the water-hemlock (Cicuta virosa,) 
is certain poison to the cow. Hence it has been called wa- 
ter cowbane, and we have heard a Fifeshire farmer, with a 
