Among the salts of milk are phosphate of lime, alkaline and other salts, and a trace of iron; so that it may be briefly said to include all the substances which the tissues of a growing animal need for their nutrition and which are required for the production of animal heat.
The yolk and albumen of eggs stand in the same relation as food for the embryos of oviparous animals, that milk does to the young mammalia; and affords another example of mixed food being provided as the most perfect nutrition. The composition of fowl’s egg is:
| White. | Yolk. | ||
| Water, | 80.0 | 53.73 | |
| Albumen, | 15.5 | 17.47 | |
| Mucus, | 4.5 | yellow oil | 28.75 |
| Salts, | 4.0 | 6.0 |
The food substances. 1. Amyloids, starch and sugars. Starch is derived from grain and vegetables, as wheat, barley, rye, oats, corn, rice, sago, tapioca, beans, peas, etc.
The vegetables contain from 75 to 90 per cent of water. Starch and sugars are derived from such as potatoes, turnips, carrots, beets, etc., etc.
The fruits are largely composed of water, sugars, and acids.
All these classes of food contain only three elements.—Starch:
| Carbon. | Hydrogen. | Oxygen. |
| 18 | 30 | 15 |
In their composition we have fifteen molecules of water presented carrying eighteen atoms of carbon. Sugar:
| Carbon. | Hydrogen. | Oxygen. |
| 12 | 22 | 11 |