
OF THE DOCTRINE OF VITAL AFFINITY. 397 
mencing the subject of Digestion in his anatomical lectures. ‘Some tell you that 
we have here a fermenting vat, and some tell you we have a stewpan, but I tell 
you we have a stomach.” And when we remember how little has been done to 
elucidate the function of digestion by likening the changes in the stomach either 
to fermentation or to chemical solution (although both are principles which 
appear to act to a certain extent), and how much comparative anatomists and 
physiologists have done, by extending their inquiries into other classes of ani- 
mals, and studying in all, the changes which commence in the stomach and ter- 
minate in the different organs of excretion—to establish laws peculiar to physio- 
logy, under which so many forms of structure, and so many vital operations may 
be arranged,—we can hardly fail to admit that this distinction was wisely drawn. 
Indeed, the whole science of Morphology, or of the analogies of the structures 
formed by living action—as it is certainly a branch of knowledge strictly swi 
generis—may be said to furnish an illustration of the advantage of keeping the 
investigation of the laws of living action entirely separate from all other scientific 
inquiries. 
But the authority to which I would wish particularly to refer, as sanctioning 
and authorising the view of the chemical phenomena of the living body which I 
here advocate, is that of Hatter, whose great achievement in physiology was 
simply that of establishing the strictly vital nature, and laying down the most 
important laws, of the living property of Contractility; the only property con- 
cerned in organic life which is expressly admitted by Dr Dauseny to be truly 
vital, but to the assertion of which the mechanical physiologists of that age were 
opposed, on grounds, as it appears to me, exactly analogous to those on which the 
doctrine of vital affinity is now opposed, because it had not been proved how far the 
_ mechanical properties of matter were, or were not, adequate to explain the move- 
ments of living bodies. 
“ As all physiology,” says Hatter, “ involves a history of motions by which 
the animal machine is agitated, and as all motions have their own laws, we can 
_ perceive why, about the end of last century, the principles of hydraulics, hydro- 
statics, and mechanics, were transferred to physiology. There is a difficulty in 
this matter, however, and if we reckon up all the good, and all the evil, which 
has been done to physiology, by the cultivation of these sciences, some may think 
that we might gladly renounce all the good, for the sake of escaping the evil. 
_ There are certainly many things in the animal economy very different from the 
effects of ordinary mechanical laws; great movements excited by slight causes ; 
the flow of fiuids hardly diminished by causes which, according to established 
mechanical laws, ought to arrest them entirely ; motions excited by unperceived 
causes ; vigorous movements produced by the contraction of weak fibres, &c. ; 
from which I do not infer, that simply physical laws are to be repudiated in phy- 
_ siology; but this I maintain, that they are never to be transferred to the eaplana- 
VOL. XX. PART III. 5P 
