But there are certain distinct and different principles which the body requires should be furnished to it, out of food. You stand there very firmly on the ground, and you look jolly and substantial enough. I should think from your appearance you have been in no way stinted in the matter of supplies. I estimate, at a guess, that your substantial body would weigh, some one hundred and fifty pounds, if placed in the scales. Now what do you think the greater part of those one hundred and fifty pounds is composed of. Bones? Not exactly, you are too soft for that. Flesh? There seems plenty of flesh, but the flesh is not the most abundant element. Brains? I am afraid they are less than the flesh. No. You will wonder indeed when I tell you that three-quarters of that firm and well-knit frame are nothing else but water. If I were to take your body and dry it until all its water was gone, there would remain behind nothing but thirty-seven pounds of dry mummy-substance, in the place of the original one hundred and fifty pounds; one hundred and thirteen pounds of water would have steamed away. You will see then that water must be furnished in fair quantity, with or in the food. You have heard, I do not doubt, many horrible and sad things which have happened when people have been kept a long time without water. Thanks to the bounty of Providence, this privation is, however, one that very rarely occurs.
But now, supposing that we have steamed away the one hundred and thirteen pounds of water, and that there are left behind thirty-seven pounds of dry substance, what does that substance consist of? It still contains several distinct things, which have had entirely distinct offices to perform in the living frame.
First, you know, there is that flesh, which makes so comely a show. Now, we shall be able to find out how much there really is of flesh. Of dry flesh-substance, including a little skin and jelly, there are seventeen pounds, and that is the working part of the frame. It is by its means the ton-weight can be lifted one mile high in a single day, and that all the moving and acting, of whatever kind, are effected. Remember, then, that the acting part of the living body is flesh-substance, and that of that flesh-substance there are not more than seventeen pounds in a full-grown man.
While your body is alive, there is a hard frame-work inside of it, upon which the soft flesh is fixed, in order that it may be kept in a convenient and durable form, and around which the water is packed in a countless myriad of chambers, and vessels, and porous fibres. The hard internal frame-work is composed of what are called bones. In the dried mummy, left when the moisture is all gone from the body, there are rather more than nine pounds of this mineral bone-substance. But there are also nearly three-quarters of a pound of other mineral substances, which were scattered about in various situations, and which were employed for various purposes. There is salt which was in the saliva, in the gristle, and in the blood. There is flint which was in the hair. There is iron which was in the blood. There is potash which was mixed with the flesh-substance. There are lime and phosphorus in the hard millstones—the teeth; and there is phosphorus, which was in the nerves and the brain. These mineral substances with the bone-earth, which is principally a kind of lime, form together the ash or dust which is returned to the ground after the body has decayed. It is the flesh-substance which flies away to become poison-vapor in the air.
But besides water to do transporting work, flesh substance to do active mechanical or moving work, and mineral substance to do passive mechanical or supporting work, there is yet another kind of material within the body. You have as much as six pounds of fat, scattered about or packed away amid the seventeen pounds of dry flesh. What can that be for? What use do you think you make of your fat? You have, I dare say, a sort of comfortable sense that it keeps you warm. You know that some of your lean neighbors cast envious eyes towards you in severe winter weather, and have chattering teeth and goose’s skins, when you are quite free from such tokens of chilliness. But you will nevertheless be surprised when I tell you what a really fiery piece of business this warming by fat is. Your fat is a store of fuel, which you are going to burn to heat your body, exactly as you burn coal in the grate to heat your room in the winter. It is oil laid by, to be consumed gradually, as a sort of liquid coal, in the furnace of the living machine. Of this, we shall, however, have to say more, by itself, by and by. For the present merely bear in mind that fat is the fuel substance which furnishes warmth to the body. It also combines with the phosphorus and with water to make up the nerve-substance and the brain-substance, which do the feeling and thinking work. These too, however, will have to be spoken of hereafter by themselves.
Let us now then take stock of the stores we have on hand, within the skin of a living body of 150 pounds weight. We have
| Water for transport and moistening | 113 | pounds |
| Flesh-substance for movement | 17 | pounds |
| Mineral-substance for support | 10 | pounds |
| Fuel-substance for warming | 6 | pounds |
| If we add these together, our sum is | 146 | pounds |
We still want four pounds more to make up our 150. Where are we to get these? Why we have got them already. Have we not already learned that there are four pounds of freshly-digested food being washed along through the supply-pipes of the body?
| We have only to add to the previous | 146 | pounds |
| Dry substance of the blood | 4 | pounds |
| and our tally is completed to | 150 | pounds |
As the blood is the direct source of supply to all the structures of the body, the material which is being poured out through the supply-pipes,—it follows that those four pounds must contain within themselves flesh-substance, mineral ash, and fuel. There are in twenty pounds of blood, sixteen pounds of water to wash along the more substantial part through the supply-pipes, three pounds ten ounces of flesh-substance, four ounces of fuel, and about two ounces of mineral matter; salt, phosphorus, lime, and the rest.