Page:Popular Science Monthly Volume 31.djvu/108

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98
THE POPULAR SCIENCE MONTHLY.

which diminish in size by frequent branching as they converge toward the top of the head. They are in a most favorable position to be compressed, lying on unyielding bone and covered by thin tissue. Consider what effect must be produced by a close-fitting, heavy, and rigid hat: its pressure must lessen to a certain extent the flow of arterial blood, and obstruct to a greater extent the return of the venous; the result being a sluggish circulation in the capillaries around the hair follicles and bulbs, a consequent impairment of nutrition, and final atrophy. This pressure is not trivial or imaginary, as any one will admit who has noticed the red band of congestion on the forehead when a hard hat is removed after moderate exercise. If the man is bald, the red pressure-mark can be seen all around the head.

It may be asked, Can the wearing of a tight band around the head for a few hours a day have any perceptible effect on the growth of the hair? That the hair-bulbs are susceptible to disturbances of nutrition is evident from the effect of a continued fever, or any wasting disease, where nutrition is seriously impaired. They (the hair-bulbs) suffer with the general system; the hair has been starved to death, so to speak, and comes out in large quantities, sometimes amounting to temporary alopecia. If the hair-crop can be thus destroyed by three or four weeks of constant lessened nutrition, it is reasonable to suppose that the same cause, though slight and intermittent, will in time produce the same result.

The course of an ordinary case of baldness corresponds with this view. We observe usually a thinning out of the hair at the poll of the head, or part corresponding to the posterior fontanelle of infancy; a patch appears two or three inches in diameter like the tonsure of a priest. Or, instead, the thinness may begin above the forehead, but in every case, the hair disappears first where the circulation is weakest—that is, along the top of the head, the region most remote from arterial force. The sparseness, at first slight, becomes year by year more apparent, and, finally, a bare and polished surface is presented which gradually descends to the hat-band and there stops. Mark this point, it never goes below the rim of the hat. I admit that the line of denudation does not in some cases correspond exactly with the hat-band; it will be noticed that the coincidence is accurate enough at the back of the head from a point opposite the top of the ear on one side to the corresponding point on the other, but in front of this on either side is often a tuft above the horizontal line that still maintains its growth. The explanation is, that the temporal muscle, occupying the hollow space in the temporal bone, acts as a cushion, thus relieving the pressure on the blood-vessels. In men with rounded heads, full in this region, a continuous line will be observed.

Before leaving this part of the subject I would direct attention to the complete change effected in the scalp after the disappearance of the hair. Unlike the thick, stiff, glandular structure it formerly was,