CHEMICAL COMPOSITION OF THE HUMAN BODY.

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Proximate Principles exist in the body under their own form, and can be extracted without losing their distinctive properties.

There are about one hundred proximate principles, which are divided into four classes, viz.: inorganic, organic non-nitrogenized, organic nitrogenized, and principles of waste.

Sodium chloride............... In all fluids and solids except enamel. Potassium chloride............ In muscles, liver, saliva, gastric juice, etc. Ammonium chloride.......................... Gastric juice, saliva, tears, urine.

Calcium chloride.......

Calcium carbonate...

Bones, teeth, urine.

Calcium phosphate

Magnesium phosphate

Sodium phosphate
Potassium phosphate
Sodium sulphate

Potassium sulphate
Sodium carbonate

Potassium carbonate

}

...

Bones, teeth, cartilage, internal ear, blood.

In all fluids and solids of the body.

Universal, except milk, bile and gastric juice.

} ... Blood, bones, lymph, urine, etc.

Magnesium carbonate......... Blood and sebaceous matter.

The inorganic principles enter and leave the body under their own form. Water is an essential constituent of all the tissues of the body, constituting about 70 per cent. of the entire body weight. It is introduced into the body in the form of drink and as a constituent of all kinds of food. The average quantity consumed daily is about four pints. While in the body, water acts as a general solvent, gives pliability to various tissues, and promotes the passage of inorganic and organic matters through animal membranes. It also promotes chemical changes which are essential to absorption and assimilation of food and the elimination of products of waste. It is probable that water is also formed within the body by the

union of oxygen with the surplus hydrogen of the food. It is eliminated by the skin, lungs and kidneys.

Sodium chloride is present in all the solids and fluids of the body, with the exception of enamel. It regulates osmotic action, holds the albuminous principles of the blood in solution, and preserves the form and consistence of blood corpuscles and the cellular elements of the tissues, by regulating the amount of water entering into their composition.

Calcium phosphate is the most abundant of all the inorganic principles with the exception of water, and is present to a great extent in bone, teeth, muscles and milk. It gives the requisite consistency and solidity to the different tissues and organs. In the blood, it is held in solution by the albuminous constituents.

The Sodium and Potassium phosphates are present in most of the solids and fluids, and give to them their alkaline reaction. They are chiefly derived from the food.

II. ORGANIC NON-NITROGENIZED PRINCIPLES.

The organic non-nitrogenized principles are derived mainly from the vegetable world, but are also produced within the animal body. They are divided into: Ist the carbo-hydrates, comprising starch and sugar, bodies in which the oxygen and hydrogen exist in the proportion to form water, the amount of carbon being variable; 2d, the hydro-carbons, comprising fats, bodies having the same elements entering into their composition, but with the carbon and hydrogen increased and the oxygen diminished in amount.

Sugar is found in many of the tissues and fluids of the body; e.g., liver, milk, placenta, blood, muscles, etc. The varieties of sugar are soluble in water, assume the crystalline form upon evaporation, and are converted into alcohol and carbonic acid by fermentation. Sugar is derived from the food, absorbed into the blood, where it largely disappears. After playing its part in the nutritive processes of the body, it is oxidized, and thus contributes to the formation of heat. It is finally eliminated under the form of carbonic acid and water. There is no experimental proof that sugar contributes directly to the formation of fat in the animal body.

The Neutral fats, when combined in proper proportions, constitute a large part of the fatty tissue of the body; they are soluble in ether, chloroform and hot alcohol; insoluble in cold alcohol and water, and liquefy at a high temperature; when a neutral fat is subjected to a high temperature in the presence of water and an alkali, it is decomposed, with the assimilation of water, into a fatty acid and glycerine. The fatty acid combines with the alkali and forms an oleate, palmitate or stearate, according to the fat used. A similar decomposition of the neutral fats is said to take place in the small intestine during digestion. When thoroughly mixed with pancreatic juice, the fats are reduced to a condition of emulsion, a state in which the fat is minutely subdivided and the small globules held in suspension.

The Fatty acids combined with sodium, potassium and calcium, are found as salts in various fluids of the body, such as blood, chyle, fæces, etc. Phosphorized fats in nervous tissue, butyric acid in milk, propionic acid in sweat, are also constituents of the body.

The Fats are derived from the food, both animal and vegetable. They are deposited in the form of small globules in the cells of the different tissues, are suspended in various fluids, are deposited in masses in and around various anatomical structures and beneath the skin. Independent of the fat consumed as food, there is good experimental evidence that fat is also produced within the animal body from a partial decomposition of the albuminous compounds. Fat serves as a non-conductor of heat, gives roundness and form to the body, and protects various structures from injury. The fats are ultimately oxidized, thus giving rise to heat and force, and are finally eliminated as carbonic acid and water.

III. ORGANIC NITROGENIZED PRINCIPLES.

The Albuminous compounds are organic in their origin, being derived from the animal and vegetable world; they are taken into the body as

food, appropriated by the tissues, and constitute their organic basis; they differ from the non-nitrogenized substances in not being crystalline, but amorphous, in having a more complex but just as definite composition, and containing in addition to C. O. H., nitrogen, with, at times, sulphur and phosphorus. The albumens possess characteristics which distinguish them from all other substances: viz., a molecular mobility, which permits isomeric modifications to take place with great facility. Under favorable conditions they promote chemical changes, by their presence (catalysis), in other substances: e. g., during digestion, salivin and pepsin cause starch and albumen to be transformed into sugar and albuminose respectively. Different albumens possess varying proportions of water, which they lose when subjected to desiccation, becoming solid; but upon exposure to moisture they again absorb water, regaining their original condition—they are hygroscopic. Another property is that of coagulation, which takes place under certain conditions: e. g., the presence of mineral acids, heat, alcohol, etc.

After death the albuminous compounds undergo putrefactive changes, giving rise to carburetted and sulphuretted hydrogen and other gases. Albumen exists in the blood, lymph, chyle, constituting the pabulum of the tissues; it is coagulated by heat, mineral acids and alcohol.

Peptones are formed in the stomach from the digestion of albuminous principles of the food; they are coagulated by tannic acid, chlorine, acetate of lead, and characterized by great diffusibility, which permits them to pass through animal membranes with facility.

Fibrin can be obtained from freshly drawn blood by whipping; it also coagulates spontaneously, and when examined microscopically exhibits a filamentous structure.

Casein is the albuminous principle of milk.

Ostein constitutes the organic basis of bone, with which are mingled the salts of lime.

Myosin is found in muscles, protagon in brain, pepsin, pancreatin and salivin, in the digestive fluids.

Mucin, chondrin, elastin, keratin and globulin, are found in mucus, cartilage, elastic tissues, hair, nails, and red corpuscles, respectively.

As the properties of the compounds formed by the union of elements are the resultants of the properties of the elements themselves, it follows that the ternary substances, sugars, starches and fats, possess a great inertia and a notable instability; while in the more complex albuminous compounds, in which sulphur and phosphorus are united to the four chief elements, molecular mobility, resulting in isomerism, exists in a high degree. As

these compounds are unstable, of a great molecular mobility, they are well fitted to take part in the composition of organic bodies, in which there is a continual movement of composition and decomposition.

These principles, which represent waste, are of organic origin, arising within the body as products of disassimilation or retrograde metamorphosis of the tissues; they are absorbed by the blood, carried to the various excretory organs, and by them eliminated from the body.

The excrementitious substances will be fully considered under excretion.

Proximate Quantity of the Chemical Elements and Proximate Principles of Body Weighing 154 lbs.

STRUCTURAL COMPOSITION of THE BODY.

The Study of the Structure of the body reveals that it is composed of dissimilar parts, e. g., bones, muscles, nerves, lungs, etc.; while these, again, by closer examination, can be resolved into elementary structures, the tissues, e. g., connective tissue, muscular, nervous, epithelial tissue, etc. Microscopical examination of the tissues shows that they are composed of fundamental structural elements, termed cells.

Cells are living physiological units; the simplest structural forms capable of manifesting the phenomena of life.

Cells vary in their anatomical constitution in the different structures of the body, and may be classed in three groups, viz.: I. Cells possessing a distinct cell wall, cell substance and a nucleus. 2. Cells possessing a cell