228 
The Applications of Physiology 
tlieiofore at the expense of the tissues of the body. Sportsmen 
who are accustomed to wander over the moors without food must 
have observed a sedimentary deposit in their urine. Exactly the 
same deposit (uric acid) takes place when a patient is afflicted 
with fever.* The cause is the same in both, — that in the absence 
of food the tissues of the body are transformed in production of 
force, and at the same time oxygen is not respired in sufficient 
quantity to convert the waste matter of the tissues into urea.f 
(Liebig.) 
If, then. It be admitted that practice confirms theory in assert- 
ing that animal heat arises from a combustion of food, and that 
the production of force, or, in other words, of motion, is always ac- 
companied by a change of matter in the body, we are prepared 
to apply these two great laws in their practical applications. And 
to save misconception, I distinctly state at the outset, that any 
suggestions which may arise from consideration of the theories of 
fattening must be received by you with caution, and looked upon 
by you with suspicion, as the suggestions of a man with a deficient 
knowledge of practice. But if, on the other hand, you find that 
practice unites with science in establishing the truth of these theo- 
ries, then I may solicit a fair hearing for the suggestions which 
they naturally produce. 
I shall divide the remainder of our subject into four parts : — 
1st. The food of cattle. 
2nd. The rearing and fattening of cattle. 
3rd. The feeding of cattle for dairv purposes. 
4th. An attempt to explain the ''fattening points" of cattle, 
and the causes of the peculiar aptitude to fatten possessed by va- 
rious breeds. 
Food of Cattle. — It has already been shown that there are 
two kinds of food. The first, which contains nitrogen, is exactly 
of the same composition as the principal tissues of the human 
body, and is the only substance which can supply the waste of 
these tissues. The second kind of food is that destitute of nitro- 
gen, such as starch, gum, and sugar, all of which are destined for 
the support of respiration and consequent heat of the animal. 
The latter kind of food, when in excess, is converted into fat, but 
never into muscle. The increase of flesh in an animal consists in 
two changes of the matter of the food, without any alteration in its 
composition. The albumen or nitrogenous constituent of the 
food is first converted into blood, without decomposition, and the 
* Fever consists in an exaltation of force, and is generally accompanied 
with loss of appetite : the tissues must therefore furnish the change of 
matter necessary for the production offeree. 
t Urea is the usual state in which the waste nitrogenous matter of the 
body is expelled from the system. 
