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XXIV. — Defence of the Doctrine of Vital Afinity. By Wi1tam PuLTENEY 
Autson, M.D., &c. &c., Professor of the Practice of Medicine in the University 
of Edinburgh. 
(Read 15th March 1852.) 
Having expressed a decided opinion that there are, in all living bodies, che- 
mical as well as mechanical phenomena, which, in the present state of our 
knowledge, ought to be designated as Vital, and referred to the operation of laws, 
distinct from those that regulate the chemical changes of inanimate matter, and 
observing that this opinion is controverted, and that the view of the chemical 
phenomena of life which I have maintained, is rejected as unphilosophical and 
delusive by two authors of high scientific reputation—Baron Humsotpr and Dr 
Dauseny,—and that the judgment of other authors of acknowledged character on 
this subject is not clearly expressed, and seems to me to involve it in unneces- 
sary obscurity, I am led to hope that some farther explanations may be of some 
use in establishing the first principles of a Science which, as it appears to me, 
has suffered, in several instances, not so much from want of facts, as from hypo- 
thetical and erroneous inferences, drawn from facts that are already known. 
When I first undertook, above thirty years ago, to deliver lectures on Phy- 
siology, I ventured to express an opinion, that “a discovery would be made, 
connecting the imgesta into the animal body with the nourishment of the different 
textures, and with the nature of the different excretions, equally important as 
illustrating the obscure chemical phenomena of the living body, and the intention 
of the different secretions, as the discovery of the circulation of the blood was, in 
ilustrating the movements going on in its interior, and the use of the organs con- 
cerned in effecting them.” It did not occur to me, nor do I know that any one 
had then conjectured, that these chemical phenomena, like the movements of the 
animal fluids, partook of the nature and formed part of a circulation, but of one 
of such extent and complexity, that the atmosphere, the soil, and the vegetable 
kingdom, furnish the other great links in the circuit, and that all the elements 
of the ancients, fire, air, earth, and water, are literally and essentially concerned 
as agents in maintaining it. 
It appears, however, from the following passage in one of the earlier writings 
of Sir Humpury Davy, that he was aware of, and had duly refiected on, the most 
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