ning. If not ostensibly employed as a means of
reaching new truths, it is at least privately appealed to for
confirmation of truths reached _a posteriori_.

But the illustrations above given go far to show, that it may to a
considerable extent be safely used as an independent instrument of
research. The necessities for a nutritive system, a respiratory system,
and a vascular system, in all animals of size and vivacity, seem to us
legitimately inferable from the conditions to continued vital activity.
Given the physical and chemical data, and these structural peculiarities
may be deduced with as much certainty as may the hollowness of an iron
ball from its power of floating in water.

It is not, of course, asserted that the more _special_ physiological
truths can be deductively reached. The argument by no means implies
this. Legitimate deduction presupposes adequate data; and in respect to
the _special_ phenomena of organic growth, structure, and function,
adequate data are unattainable, and will probably ever remain so. It is
only in the case of the more _general_ physiological truths, such as
those above instanced, where we have something like adequate data, that
deductive reasoning becomes possible.

And here is reached the stage to which the foregoing considerations are
introductory. We propose now to show that there are certain still more
general attributes of organized bodies, which are deducible from certain
still more general attributes of things.

* * * * *

In an essay on "Progress: its Law and Cause," elsewhere published,[8] we
have endeavoured to show that the transformation of the homogeneous into
the heterogeneous, in which all progress, organic or other, essentially
consists, is consequent on the production of many effects by one
cause--many changes by one force. Having pointed out that this is a law
of all things, we proceeded to show deductively that the multiform
evolutions of the homogeneous into the heterogeneous--astronomic,
geologic, ethnologic, social, &c.,--were explicable as consequences. And
though in the case of organic evolution, lack of data disabled us from
specifically tracing out the progressive complication as due to the
multiplication of effects; yet, we found sundry indirect evidences that
it was so. Now in so far as this conclusion, that organic evolution
results from the decomposition of each expended force into several
forces, was inferred from the