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Page:Popular Science Monthly Volume 54.djvu/831

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IRON IN THE LIVING BODY.

Antilles, and continue to multiply like our American pension claimants. The hunters of those jungle woods, indeed, must often smile to remember the complaint of the early settlers that the pleasure of the chase in the West Indian wilderness was modified by the scarcity of four-footed game, and in the total number (as distinct from the number of species) of wild or half-wild mammals Cuba and Hayti have begun to rival the island of Java.

 

[To be continued.]

 

IRON IN THE LIVING BODY.
By M. A. DASTRE.

IRON occurs, in small and almost infinitesimal proportions, in numerous organic structures, in which its presence may usually be detected by the high color it imparts; and in the animal tissues is an important ingredient, though far from being a large one. It is essential, however, that the animal tissues, and particularly the liquids that circulate through them, should be of nearly even weight, else the equilibrium of the body would be too easily disturbed, and disaster arising therefrom would be always imminent. Hence the iron is always found combined and associated with a large accompaniment of other lighter elements which, reducing or neutralizing its superior specific gravity, hold it up and keep it afloat. Thus the molecule of the red matter of the blood contains, for each atom of iron, 712 atoms of carbon, 1,130 of hydrogen, 214 of nitrogen, 245 of oxygen, and 2 of sulphur, or 2,303 atoms in all. Existing in compounds of so complex composition, iron can be present only in very small proportions to the whole. Though an essential element, there is comparatively but little of it. The whole body of man does not contain more than one part in twenty thousand of it. The blood contains only five ten-thousandths; and an organ is rich in it if, like the liver, it contains one and a half ten-thousandths. When, then, we seek to represent to ourselves the changes undergone by organic iron, we shall have to modify materially the ideas we have formed respecting the largeness and the littleness of units of measure and as to the meaning of the words abundant and rare. We must get rid of the notion that a thousandth or even a ten-thousandth is a proportion that may be neglected. The humble ten-thousandth, which is usually supposed not to be of much consequence, becomes here a matter of value. Chemists working with iron in its ordinary compounds may consider that they are doing fairly well if they do not lose sight of more than a thousandth of it; but such looseness would be fatal in a biological