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XIII. — An Essay on Fat and Muscle. By W. F. Karkeek, 
Veterinary Surgeon, Truro. 
Prize Essay. 
I. The object of this essay is to endeavour to explain " the 
causes which appear to determine the production of fat and 
muscle respectively, according to the present state of our know- 
ledge of animal physiology." Formerly, the study of the uses 
and functions of the different organs, and of their mutual con- 
nexion in the animal body, was the chief object of physiological 
researches; but although these yielded the most valuable results 
in relation to the recognition of dissimilar forms and conditions 
to be found in healthy and diseased structures, yet they afforded 
no conclusions calculated to give us a more extensive insight into 
" the essence of the vital processes." The recent alliance of 
chemistry with physiology has furnished most valuable data both 
in this respect and as regards the nutritiveness of particular 
vegetables in the feeding of our domesticated animals. The most 
important discoveries in this branch of science are those of Pro- 
fessor Liebig, he being admitted, by the unanimous voice of 
European chemists, to be the first living authority on Organic 
Chemistry. Professor Playfair was the first English chemist who 
attempted to apply those discoveries to the practical purposes of 
the fai mer — holdnig up the torch of science, as it were, to the 
agriculturists, and teaching them the advantages to be derived from 
the union of practice with science.* It will be seen, in the 
course of this essay, that we have adopted many of the physio- 
logical views of Professor Liebig ; and if we have succeeded in 
adding but one useful fact to the mass of knowledge already ac- 
quired, which may be advantageously put into practice in the 
ordinary operations of a farm, our object will be sufficiently 
realised. 
2. Your attention will first be directed to some of the phe- 
nomena connected with nutrition and ffrowth. When we consider 
that the food of vegetables and animals is either altogether dif- 
ferent from their substance, or passes before being assimilated 
into a new form, we must admit that the nutrition and growth of 
both depend on chemical agencies, although these operate under 
peculiar conditions, and are influenced by the unknown force 
which is called the vis vita;, or vitality, so as to produce results 
that cannot be imitated by the chemist. Tlie food of vegetables 
is derived from the crude and simple materials which they absorb 
from the air, the earth, and the waters. These, after being con- 
* Playfair's Lectures before the Members of the Royal Agricultural 
Society, December, 1842. 
