It is of more interest, however, to inquire into the general causes which are at work in bringing about this unwelcome change. The fact is familiar that in the large majority of cases we find, on examining a head about becoming gray, that single hairs are gray throughout their whole length, while others retain their original color. We do not find a hair black at the extremity and white at the root, as we might expect, nor do we find others passing through the intermediate hues between gray, and that natural to the person. What we do find is a single, long, silvery thread, winding conspicuous and ominous among the raven tresses.
This is because when a hair turns gray it loses its pigment promptly—in a few hours or a few days throughout its whole length—owing to absorption by the root, or some chemical or mechanical change in the hair itself.
There are some persons who turn gray very early without visible cause, and in some families premature grayness is hereditary. Sometimes a single lock of the hair, or one spot on the head, alters in color, while all the remainder is unchanged. To explain such vagaries is not easy.
Very respectable authorities say that when gray hair falls out, it does not grow again. This may be the rule, but we have known exceptions to it. A lady of our acquaintance lost all her hair, which was gray,
