GT2 AN ESSAY ON EAT AND MUSCLE. 
and renovation, absorption and nutrition, are always being carried 
on concomitantly. Now, within certain limits it is observed that 
the greater the waste, the greater is the supply, as by constant 
exercise the muscles are increased instead of decreased, so that 
the effect of nutrition is not only to replace what was destroyed, 
but to supply a certain quantity more. And again, by the same 
law, an organ that was originally intended to perform a certain 
function, 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 in- 
ternal 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 intestines, 
are also considerabl} r smaller in extremely fat animals than in lean 
ones of the same age and breed. In the intestines this is par- 
ticularly observable — the circumference of the tripe is considerably 
reduced, but it is thicker and richer. This change appears to take 
place more rapidly during the latter stages of fattening; 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 exhalents 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. 
The breeder may learn a very important lesson from these re- 
marks ; for if it be true ( and time and observation will prove them 
to be soj 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 
