No precise experiments have yet been made with the view of determining how much saline matter is daily excreted from the body of a healthy man, or in what proportions the different inorganic substances are present in it; but it is satisfactorily ascertained, that without a certain _sufficient_ supply, the animal will languish and decay, even though carbon and nitrogen in the form of starch and gluten be abundantly given to it. It is a wise and beautiful provision of nature, therefore, that plants are so organized as to refuse to grow in a soil from which they cannot readily obtain a supply of soluble inorganic food, since that saline matter which ministers first to their own wants is afterwards surrendered by them to the animals they are destined to feed. Thus the dead earth and the living animal are but parts of the same system,—links in the same endless chain of natural existences,—the plant is the connecting bond by which they are tied together on the one hand,—the decaying animal matter which returns to the soil, connects them on the other. 4. The solid bones of the animal are supplied from the same original source,—the vegetable food on which they live. The bones of the cow contain 55 per cent. of phosphate of lime, of the sheep 70, of the horse 67, of the calf 54, and of the pig 52 lbs., in every hundred of dry bone. All this must come from the vegetable food. Of the bone-earth also, a portion,—perhaps a variable portion,—is every day rejected from the animal; the food, therefore, must contain a daily supply, or that which passes off will be taken from the substance of the bones, and the animal will become feeble. It is kindly provided by nature, that a certain proportion of this ingredient of bones is always associated with the gluten of plants in its various forms,—with the fibrin of animal muscle and with the curd of milk. Hence, man, in using any of these latter along with his vegetable food, obtains from them, with comparative ease, the quantity of the earth of bones which is necessary to keep his system in repair; while those animals which live upon vegetables alone, extract all they require along with the gluten of the plants on which they feed.