The higher mammalian bodies - and the same applies with some qualifications to most animals and plants - are composed of fifteen essential elements, in various combinations. Other elements are occasionally present from medication, poisoning of a degree insufficient to interfere with life, and accidental impregnation with minerals of the particular locality. Arsenic, bismuth, copper, mercury, bromin, lithium are the commonest examples. Persons living near the sea have more iodine in the thyroid than those living inland.

Elementary Composition Of Human Body

(After Moss.)

Carbon, hydrogen and nitrogen are not at all assimilable in the elemental form and act only mechanically when introduced.

Elemental phosphorus and sulphur have a medicinal, the former a toxic action. Small proportions, however, are oxidized into the form of phosphates and sulphates, respectively. Inorganic compounds act medicinally, and to form inorganic constituents of bone, etc., and to aid in various osmotic processes. Possibly small proportions are further altered to form organic combinations. As constituent parts of protoplasm, they must be mainly, perhaps entirely, ingested in similar organic compounds.

Oxygen is regularly introduced into the body in large amount both as an essential constituent of organic foods and as an element by respiration. In the latter form, probably always with the assistance of enzymes, it oxidizes all forms of organic components of the body, but probably always destructively rather than constructively.

All the other elements might, barring corrosive action, be administered in the elemental state, and would, thereupon, form inorganic and organic combinations in the alimentary canal similar to what would be formed in vitro with the same available substances for combination. Iron can certainly be assimilated in this way, though not so readily as from organic compounds. In most instances, however, all of these elements are best given as salts or as organic compounds.

Excepting the inevitable reactions in the alimentary canal, which have no vital significance, it may be stated that no element can be used as a nutriment in the elemental state.

Proximate principles are chemic compounds of which the body is composed and into which it is theoretically - but not analytically - separable without chemic change. They may be classified as follows:

Disregarding unassimilated ingesta and excreta, including, under these heads, the gases of the blood, etc., a very lean human body is composed of proximate principles in the following proportions.:

(Ordinarily 9 - 23%, on the average 16%, in obesity 50%.)

(More thanhalf in blood, remainder in muscle plasma, spleen, liver, etc.)

These proportions are, of course, subject to great variation, especially in regard to fat, which correspondingly reduces the proportion of the remaining constituents.