The chemical elements found in the body and their general compounds are shown in the two following tables :

Chemical Elements Of The Body

Oxygen

Hydrogen

Carbon

Nitrogen

Calcium

Phosphorus

Potassium

Sodium

Sulphur

Chlorine

Silicon

Iron

Magnesium Fluorine Iodine Lithium

Constituents Of The Body

Water

Nitrogenous matter Fat

Mineral matter Carbo-hydrates Acids

Water supplies from about two-fifths to four-fifths of the entire weight of the body; the percentage being affected by various conditions, of which age is as a rule the principal. The proportion of water is highest at birth, and lowest in old age.

Nitrogenous matter is that in which nitrogen is found. It is divided into several classes, the discussion of which comes more within the province of physiology than within that of stable management. One or more of these forms of nitrogenous matter enter into the composition of every tissue (muscles, nerves, and glands for instance) and fluid (blood, saliva, and gastric juice for example) which are actively engaged in vital work, and into that of bones, cartilage, tendons, ligaments, skin, hair, hoofs, etc. The nitrogenous matter of muscle has, according to Hoppe-Seyler, the following composition:

Fat, the amount of which varies greatly in different animals, has the following average composition :

Mineral matters form about one-twentieth of the entire weight of the body, and are chiefly found in the bones, seven-eighths of the mineral matter of which consists of phosphate of lime, the remainder being carbonate of lime, with traces of magnesia, fluoride of lime, and common salt (sodium chloride). Small quantities of lime exist in the muscles and other soft tissues and in the fluids of the body. The percentage of lime in the body varies directly as the age of the animal. In fact, age may be regarded as the gradual calcification of the organism, which in extreme senility renders the performance of the vital functions impossible. Although salts of potash and those of soda (chiefly in common salt) constitute only about 1/3000 of the entire weight of the animal, they play an indispensable and active part in nutrition; and as they become rapidly excreted, a continued supply of them is necessary for health. Chlorine, besides being a component of common salt, is also one of hydrochloric acid (HC1), which is found in gastric juice. Silica appears in minute traces in the body; its chief office being to give hardness to the tissues in which it is present. Although iron does not add more than one ounce to the entire weight of the horse, its presence in the colouring matter of the blood is essential to life; and its due supply, to health.

The principal carbo-hydrates, which are found only to a small extent in the body, are animal starch (glycogen), dextrose (grape sugar), and milk sugar. We find traces of grape sugar in the blood, and considerable quantities of glycogen in the cells of the liver, from which it is removed by the blood in the form of grape sugar. The grape sugar preserves its identity in the circulation for only a short period.

Phosphoric acid and lactic acid, in small quantities, are the chief acids which are distributed throughout the tissues and fluids of the body. Hydrochloric acid, as just stated, is found in the gastric juice.

There are other organic compounds which are met with in the system; but their quantity is so insignificant, that they need not be mentioned.