THE MOST IMPORTANT THING IN THE BODY—A BARREL OF 9½ GALLONS OF WATER.
Starch and fat supply fuel both in reserve and for immediate consumption. They are only so much carbon, oxygen, and hydrogen mingled in certain proportions and pretty similar to sugar. But they go through curious careers in the body. Most of the fat that one swallows, for instance, meets an alkali in the intestines that has come there specially from the liver and pancreas to make soap.
In the average man some tons of excellent soap are made in a life-time, and at times there must be quite a large cake of soap in the intestines. A quantity of glycerine is also formed as a by-product, just as in a regular soap factory. The body can itself make fat. If you give it lean meat, or starch, or sugar, it will take them as raw material and manufacture good fat.
Starch, a most important constituent, goes through strange transformations. When you swallow a potato it is chiefly starch; that is, six atoms of carbon to ten of hydrogen and five of oxygen. In the intestines a little water is added and it becomes sugar, for sugar is merely starch and water joined together. It goes into the blood as sugar, not being able, in fact, to get through as starch, and then it either burns up in the tissues or goes to the liver, where it drops the water and becomes a kind of starch.
The moment one feels hungry this glycogen changes into sugar again, enters the blood, and is burned up, like a candle, into carbonic acid and water. Sugar in the body is like loose cash in the pocket—it does not stay long; and there seldom is a bowlful of it. But, in some extraordinary way, if the body wishes to be saving, it sometimes converts the sugar into a substance called inosit, which, though sweet, is insoluble in water, and can, therefore, remain a long time in the liver, spleen, lungs, and muscle, being very abundant in the muscle of drunkards.
There are many other compound substances in the body. Alcohol is found in blood, bile, muscle, and brain; gum in the glands that make saliva, and in the lungs; pepsin, that digests food, in the stomach; one or two ferments, like yeast; and the pigments that colour the hair and the eye. None of these higher compounds is put together by the body. It never takes the elements and builds them up. It can only break down complex things into less complex things.
But it does one kind of manufacturing or constructive work, using complex and ready-made substances, that is amazing. No one who has eaten a cutlet, a sweet-bread, a kidney, a piece of liver, heart, tongue, and tripe, need be reminded how various are the different organs in composition. All this variety, however, the body brings about itself, marvellously selecting from the one raw material, blood, the different substances and the appropriate quantities for each kind of tissue.
Out of the blood the body takes the compounds containing calcium, phosphorus, oxygen, hydrogen, carbon, and some other things, for the making of the skeleton. The skeleton exists for the sole purpose of giving support to the other parts, and forms 14 hundredths, or about one-seventh, of the body-weight in a man, and 13 hundredths, or about one-eighth, in a woman.
Thus a man of ten-stone-ten would have to carry a skeleton weighing 21 lbs.—that is, while quite fresh. When dry it would weigh only 12½ lbs. In a woman of eight stone the weights would be 14 lbs. and 8½ lbs. respectively.
To make muscle, the body takes other substances in appropriate quantities from the blood. Whether you are weak and powerless, or fit to form one of an Oxford eight and to lift weights with Sandow, depends, to a considerable extent, on the selective skill of your blood.