An Essay on Fat and Muscle. 
257 
to supply a certain quantity more. And again, by the same law, 
an organ that was originally intended to perform a certain func- 
tion, if that function be not fulfilled, will diminish in size and 
power. In the muscular arm of a blacksmith, and the delicate 
arm of a person not accustomed to labour, we have an excellent 
example. Now, whatever is true of the external parts is likewise 
true of the internal parts of the body. If we take for an example 
the heart of a calf, which must increase in size as it increases in 
growth — it increases, not only in its whole bulk, but also in the 
size of the cavities. If an addition were made only to the exterior 
of the heart, its whole bulk would be increased, but the size of 
the cavities would be proportionately small. We must therefore 
assume that substance is removed from the interior of the heart, 
at the same time, though perhaps not exactly in the same quantity, 
that substance is added to the exterior. In like manner, when 
the heart of a man diminishes in size, as it does in consumption, 
materials must be abstracted from the exterior, and added in rather 
a less proportion to the interior. It is upon this principle that 
in proportion as animals fatten, particularly stall-fed ones, their 
internal organs become smaller — the lungs adapt their size to the 
volume of oxygen consumed, and the liver becomes smaller as 
the secretion of bile is diminished ; the kidneys, stomach and in- 
testines are also considerably smaller in extremely fat animals than 
in lean ones of the same age and breed. In the intestines this is 
particularly observable — the circumference of the tripe is consi- 
derably reduced, but it is thicker and richer. This change ap- 
pears to take place more rapidly during the latter stages of fatten- 
ing ; and it is rather a remarkable coincidence that the fatter an 
animal becomes at this period, the less food it consumes. When 
the animal arrives at this last stage of fattening, the arterial 
action is much slower than before — a sluggish action appears to 
prevail throughout the whole vascular system, and the arterial 
exhalants appear to be engaged chiefly in manufacturing fat. If 
the animal be bled at this time, which is usually the case on the 
evening previous to its being slaughtered, very little blood can 
be drawn before it faints. 
17. The breeder may learn a very important lesson from these 
remarks; for if it be true (and time and observation will prove them 
to be so) that in proportion as an animal increases in fat will the 
organs of nutrition become diminished in size, it follows that, by 
pursuing the system of breeding from fatted animals, or from 
those having a great tendency to fatten, function must react o;i 
organization, and at last those qualities become, not only in- 
creased, but fixed in the race. By function reacting on organiza- 
tion, is meant — when an organ, as the lungs, for instance, be- 
comes diminished in consequence of not performing its natural 
VOL. V. s 
