yp PHILOSOPHY OF ZOOLOGY. 
and it is capable of being divided or multiplied by the process 
of generation. In the various kinds of organized bodies, it ex- 
hibits its different qualities, according to the structure of the 
fabric which it animates; hence we must conclude, either 
that the same principle is modified by the substances which 
it pervades, or that there are many different kinds. If we 
adopt the practice of the chemist, when examining the ele- 
mentary bodies, and their combinations, and consider those 
substances distinct in kind, whose affinities and appearances 
are different, we must conclude, that there are different 
kinds of vital principles, distinguished by different affinities 
for the various kinds of inorganic matter, and forming, 
with these, combinations, whose peculiar characters are ob- 
vious and precise. In all organized bodies, we witness an 
origin, progress and termination; but, in each species, 
these circumstances exhibit some peculiarity which is not 
observable in any other species. We are, therefore, led to 
conclude, that there are as many different kinds of vital 
principles, as there are species in nature. Hence all the 
knowledge which we possess regarding the structure and 
functions of different kinds of organized beings, is, in fact, 
a knowledge of the attributes of the different vital princi- 
ples from which these have originated ; and our systemati- 
cal arrangements, an attempt towards their classification. 
Even the vulgar, talk of the life of plants as distinct in 
principle from that of animals, although they seldom carry 
their views on this subject so far as to admit of any inferior 
division. 
II. Conditions necessary for the Existence of the Vital 
Principle.—It is, doubtless, a curious subject of mquiry, 
to ascertain those conditions which are necessary to the 
display of this principle of life, or the circumstances under 
which it is generated or excited to action. Our knowledge 
of organized bodies, however, is still too imperfect to en- 
