Perhaps the cynic might reply to this question that women’s hair
does not turn grey any more--there are too many good “tinting”
and “retouching” lotions on the market! But this answer is merely
superficial--as all cynical answers are. Hair _does_ continue to turn
grey, and the discovery of the reason is of great scientific interest.
It is hardly necessary to say that human hair is of various colors,
because of the coloring matter which it contains within its hollow
shaft. This coloring matter is its “pigmentation,” and is golden,
brown, black, etc., as the case may be, or combinations of various
simpler colors. When the hair turns grey or white, the hair remains,
but the pigmentation is somehow removed. Where has it gone, and how?
Various answers to this question have been suggested. Professor
Metchnikoff suggested that the coloring matter in the hair was
gradually eaten up or consumed by “phagocytes,”--which are hungry
cells, that attack and devour any weakened and devitalized cells or
tissues in the body. It is said that the particular cells, in this
case, are situated in the central shaft of the hair, and when they once
become active, they proceed to devour all the pigment within their
reach! In this manner the hair gradually turns grey and finally white.
This theory may be true in a number of cases--probably the
majority--but it certainly fails to account for many instances, in
which hair has been turned white, or blanched, over night, as the
result of worry or fear. In these cases, strong emotion has produced
the change. Science cannot as yet explain how this comes about, and
this sudden blanching of the hair is yet a mystery. In the majority of
cases, however, the pigment in the hair is undoubtedly consumed.