The question, “Why is my hair turning gray?” is asked in various tones of voicewhining, angry, a “how am I going to remedy it?” tone, and sometimes, as we do here, in the calm, inquiring mood of information seeking.
In whatever tone you ask it, you are not likely to have a very satisfactory answer. The question itself is capable of being split up into several:
First, what is the purpose nature has in turning the hair gray? Animals change the color of their coats seasonally, and become gray or white in the winter, but it is easy to see this is protectivetheir white fur makes them harder for their enemies to see against the snow. No such design can be ascribed to the graying of human hair.
Second, of what is it a sign? Not always age. Complete graying of the hair in the thirties and forties is common, as conversely is the retention of a great deal of pigment in certain very old individuals. The fact, however, that the atrophy of the pigment mechanism in the root of the hair shaft could go with other aging processes is obvious, and in accord with the average facts. Premature gray hair is certainly an hereditary trait. No part of the body, in fact, responds to the laws of heredity more closely, or, at least, more obviously, than the hair.
Third, what is the exact mechanism? Here we may learn some-thing from comparative biology. The whiteness of a lily is due to the complete reflection of light from air-containing vacuoles between the cells of the perianth. If we press the petal of a lily so that all the air is squeezed out, it will no longer be white. A white feather is likewise full of gas bubbles, which act like a myriad of little mirrors.
An animal may change the color of its coat in one of two ways. In those animals who change to white in winter, the new coat begins to come in during the early fall. The short white hairs can be seen growing beside the colored ones. Later the colored hair begins to shed. The process then is a replacement.
The process of hair turning gray as a part of aging is not a replacement, and the mechanism is apparently twofold. First, the pigment cells are removedby phagocytes action, according to Metchnikofffrom the region of the hair roots. Then the hair shafts become filled with very minute air bubbles. The phenomenon of whiteness here, then, is dependent upon the same structure as causes the whiteness of the lily petal, the feather, the hair of the white rat. The reason some “gray” hair is yellowish is that the hairs are coarser and the air bubbles larger: very white hair is fine and silky.
Hair turning white in a single night has some authentication. It is due to the sudden development of air bubbles.
The fourth question is what to do about it. And the only answer is to grin or dye it. There is nothing to be ashamed of in dyeing it; for many employed women who do not wish to appear superannuated it is an economic necessity.