If his mind is more particularly directed to the specific description,
discrimination, classification, and distribution of animals, he is
termed a zoologist.

For the purpose of the present discourse, however, I shall recognise
none of these titles save the last, which I shall employ as the
equivalent of botanist, and I shall use the term zoology as denoting
the whole doctrine of animal life, in contradistinction to botany, which
signifies the whole doctrine of vegetable life.

Employed in this sense, zoology, like botany, is divisible into three
great but subordinate sciences, morphology, physiology, and
distribution, each of which may, to a very great extent, be studied
independently of the other.

Zoological morphology is the doctrine of animal form or structure.
Anatomy is one of its branches; development is another; while
classification is the expression of the relations which different
animals bear to one another, in respect of their anatomy and their
development.

Zoological distribution is the study of animals in relation to the
terrestrial conditions which obtain now, or have obtained at any
previous epoch of the earth's history.

Zoological physiology, lastly, is the doctrine of the functions or
actions of animals. It regards animal bodies as machines impelled by
certain forces, and performing an amount of work which can be expressed
in terms of the ordinary forces of nature. The final object of
physiology is to deduce the facts of morphology, on the one hand, and