398 PROFESSOR ALISON’S DEFENCE 
tion of phenomena of living bodies, unless their Eualinaiiont is confirmed by experi- 
ment.” —(Phys. Prin., p. 6.) 
It might have been perfectly fairly argued at that time, that physiologists did 
not understand all the conditions, under which the laws of mechanics and of hy- 
draulics (admitted to have a certain influence) act in a living body, and that until 
it was ascertained that these would not suffice for the explanation,—that there was 
some residual phenomenon of life not capable of being so explained,—the exposition 
of any laws of motion peculiar to living bodies was premature. But Hauer did not 
think it incumbent on him to prove this negative proposition, before announcing 
the laws of muscular irritability as distinguished from any merely physical cause 
of motion ; and I believe we shall all now admit, that if he had thought this 
incumbent on him, the greatest impulse which the science of physiology received 
during the last century, would have been long, and perhaps indefinitely, post- 
poned. 
Fortified by these authorities, as well as by some formerly quoted, I again 
assert, that the only truly scientific view to be taken of this department of Phy- 
siology is, that its object is to ascertain, by the method of induction, to use again 
the expressions of Professor WHEWELL, “ when, and in what manner and degree, 
chemical as well as mechanical agencies are modified, overruled, or counteracted 
in living bodies, by agencies which must be hyper-chemical as well as hyper- 
mechanical ;” and I farther maintain, that the term Vital Affinity is as accurate a 
term as can be employed as a general expression for these agencies; that, like all 
other general principles in nature, we may expect it to act according to general 
laws, and that several of these laws, to which I have referred in this and former 
papers, are already ascertained, at least, in so far as to shew that the subject is 
one of legitimate inquiry. 
I am aware that it may be still said that this dispute is only a verbal one, 
and can have no practical or even strictly scientific application. But in answer 
to this I would observe, that so long as we adhere to the supposition, that there 
is nothing truly vital or peculiar to living bodies in their economy (as regards 
their organic functions), except motion, and that motion derived from contraction 
of solids and impulse, the notions that we can form of the nature of these functions 
in health, and of the deviations from that state in disease, must necessarily be erro-_ 
neous, because we shall always be looking in the wrong direction for the cause of 
these phenomena; and that at this precise point the most plausible medical 
theories of the last, and even of the present age, have gone astray. This, I think,, 
is sufficiently illustrated by the example already given, of the ingenuity of Dr 
Murray wasted in the invention and defence of the hypothesis which ascribed 
the secretions of animals to varying impulse on their fluids from contracting 
solids; and I shall only add a single illustration of the same kind drawn from 
the science of Pathology, and from the most fundamental of all inquiries in it, 
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Bia te oe, 
