130 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS papillary hair. Simultaneously, the walls of the lower third ot the follicle collapse on each other and the papilla shrinks while the lower end of the separated hair widens out and becomes broom-like. The hair continues to grow while attached to the hair bed and finally its in- creased size pushes it farther and 'farther up the follicle until it reaches a point just below the opening of the duct of the sebaceous gland. At this point, it is no longer nourished by a vascular supply so it stops growing, separates itself and falls out. According to Unna (2) the blood supply of the follicle con- trols nicely the growth and subse- quent shedding of the hair. In normal scalps after an interval, the papilla starts to regenerate and a new hair gradually rises in the follicle t6 push the old hair up ahead of it or less often it grows alongside of the bed hair. It is believed that the same papilla produces hair throughout life and that a new papilla is rarely produced after puberty. It is thought that this regeneration is caused by the supply of blood to the papilla and though we understand the mechanism of the a•ctual shedding, we have no idea what controls the blood supply of the papilla and follicle. Here we lack vital basic information that is of the utmost importance in the maintenance of good hair growth, If it is true that new papillae are rarely formed after puberty, the old ones must be preserved and kept healthy if we are to continue to grow hair. What do we know about growing hair and what factors influence the rate of hair growth? Surprisingly enough, we have practically no ac- curate basic knowledge on these fundamental points. Heredity is known to be of importance. How- ever. there is no sharp line of de- marcation between what is normal and what is abnormal, the same physical trait may have different meanings in two persons. For ex- ample, a full beard has a different significance to a white man than ' to an Indian• While it is recognized further that the tendency to premat- ure baldness appears to be familial and hereditary, no additional light as to why this occurs or how it is brought about is gained from that observation. Vascular and nervous factors are of basic importance. The regula- tion of the blood supply to the folli- cle is no doubt under control of the sympathetic nervous system and thi• in turn is intimately related with the central nervous system. The effect of emotional factors on hair loss and the graying of hair as seen in alopecia areata and achro- motrichia is, of course, well known. A striking example was reported by Barabal and Freeman (3) in the case of a 38-year-old white soldier, who, following a three-mile hike in De- cember, 1943, developed a sudden sharp pain in the left chest and fainted. Examination revealed no organic disease. During that night he was restless and tense and felt as though he were on the verge of a "nervous breakdown." The next

THE DERMATOLOGIST LOOKS AT THE HAIR PROBLEM 131 morning he found that his dark brown hair had turned white with the exception of a few strands and within the next few days, there occurred a considerable loss of frontal, marginal, and facial hair. While extreme examples of this type are rare, less pronounced cases are undoubtedly not too in- frequent. The question of graying of hair will be referred to again. The endocrines appear to be in- volved in hair growth in some man- ner. The glands which seem most important are the suprarenals, gon- ads, thyroid, and the pitui-tary. The latter two may not have any real direct effect, but may react on the suprarenals which in turn in- fluence the hair. The thyroid is said to particularly affect the hair of the scalp, eyebrows, and eye- lashes. The ovary and testes in- fluence the development of pubic and axillary hair, the testes, the body hair and beard. The hypoph- ysis and suprarenal through in- fluence on the testes indirectly in- fluence hair generally except the capillus, eyebrows, and eyelashes. According to Hamilton (4) common baldness (alopecia) is a sequela of sexual maturation and is, in most instances, induced by stimulation from male hormone substances. In keeping with this physiological re- lationship, the incidence of the disease is much higher in males than in females, and extensive forms of the disease are restricted almost entirely to males. Most women with pronounced forms of the disease are those with virilism. Apparently, age is a factor in the rapidity with which areas of de- nudation extend. In eunuchs, sus- ceptibility to such loss of hair can increase with age, but baldness does not occur because of inadequacy of testicular secretions. This increased susceptibility accumulates, unspent, like money in the bank, and later treatment of the eunuchs with an- drogens results in a rapid loss of hair. Available evidence does not bear crucially on the question of whel•her or not there is, with in- creasing age, a lowering of the amount of androgenic stimulation required to produce baldness. The third factor known to be in- volved is inheritance. No amount of androgenic stimulation produces baldness in persons who lack an in- herited tendency to this disease. The realization of this tendency de- pends, however, upon androgenic stimulation, since, whatever the inheritance, baldness does not ensue without androgenic stimulation. Local areas of the skin play a dominant role in the atrophic changes that result in baldness. Application of androgens directly to a local area results in piliary changes limited to that region. At the present stage of our informa- tion, it must be assumed that andro- gens are only one of what might be a family of agents (although they are the usual one) which may be cap- able of inducing atrophic changes in s•ecific areas. The degree of atrophy is controlled by the local area of skin and does not result from external changes in vascularity