44 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS "AGE, SEX AND GENETIC FACTORS IN THE REGULATION O• HAIR GROWTH IN 1V•AN: A COMPARISON OF CAUCASIAN AND JAPANESE POPULATIONS" JA•s B. D•pt. of .tintomy, Stat• Uniw•sity of N•w York, Coll•g• of Medicin• at N.Y. City, Brooklyn, New Yor•. Techniques have been devised • to provide repeatable quantitative measure- ments of hairs and their rate of growth in certain regions of the body. Using these methods, data have been obt•ned for each sex throughout the life span in Caucasian and Japanese populations. The standards constructed from these values can serve to assess some aspects of physiologic age, and to study endocrine status. They will also be valuable in gaining further under- standing of the nature and interdependence of endocrine, ageing, genetic, environmental and other regulatory factors. Beard growth, in Caucasian as compared with Japanese males, was found to be considerably greater and values reached a peak at an earlier age. This was shown by measurements of weight of hair grown per day, and was associated with higher values in Caucasians for area of skin with coarse hairs and for number of such hair per sq. cm. of a standardised region of the cheek. In a large series of Japanese females no instance of facial hirsutism was found in contrast to the high incidence reported for Caucasian women. Males of both ethnic groups had similar values for the mean diameter of coarse hairs and of their component parts and for the percentage of grey hairs with advancing age. Growth of axillary hair was also more pronounced in Caucasian than in Japanese males of comparable sex and age. The disparity between the two ethnic groups in values for axillary hair was even greater in females than in males. These data for beard and axillary hair are in the same direction and extend previous reports of greater tendencies on the part of Caucasian males to develop coarse hairs on the external ears, to become bald and to develop ache. As a rule some of the late sequelae of sexual maturation were among those which tended to occur more frequently, and to progress further in Caucasians than in Japanese. This principle seems to apply to the areas with coarse hairs in the axilla and beard as well as to the severe forms of common baldness, and it may apply to ache. Secondary sex characters and certain sex-differing pathologic states failed to develop in men who did not mature sexually. The degree to which maintenance of these conditions, once fully developed, depended upon gonadal secretions, differed among the items studied these, listed in decreas- ing order of dependence, a• e the axillary hair, beard, and common baldness. Under ordinary conditions these traits are dependent upon gonadal secretions for development, and in some instances for maintenance, but this

ABSTRACTS OF PAPERS ON THE BIOLOGY OF HAIR GROWTH 45 endocrine stimulation tends to act in a trigger-like fashion. The extent to which these states develop, and even the occurrence of certain sex-selective pathologic states, is regulated chiefly by inheritance and ageing. Studies of twins and members of large familie% supplemented by comparisons of Caucasians and Japanese (including Japanese living in Tokyo, U.S., New York), delineate and emphasise the large measure of coptrol exerted by genetic factors. Endocrine indicators of the quantitative type employed in these studies are thus to be regarded as somewhat analogous to the comb in fowl, reflecting not only the nature and type of the existent endocrine stimulation but also the vitally important responsiveness both of target organs and the organism. The inter-relations of endocrine, hereditary and ageing factors observed in studies of the beard seem relevant to growth of hairs in other regions such as eyebrow, nasal vestibule, external ear, and much of the body with the excep- tions of scalp, axilla, and pubis. The mean age-curves for axillary hair conform more closely than those for beard to the waning of gonadal secretions, as judged by titres of urinary androgens and ketosteroids. Secondary sex characters merge almost indistinguishably x•.ith male- selecting pathologic states like common baldness and the severe forms of ache. There are suggestions that this spectrum may extend to some of the more lethal male-selecting pathologic states and to the shorter duration of life in males than in females in man and other species. It is of considerable interest, therefore, that in some aspects the modes of control of piliary secondary sex characters seem to be analogous, and may provide insight to those of certain sex-selecting pathologic states. "HORMONAL FACTORS' • M•.LV•N P. MOHN Dept. of Anatomy, State University of New York, 450 Clarkson Ave., Brooklyn 3, 2Vew York. Previous investigations on the effects of hormones on hair growth have been limited to observations on the spontaneous replacement of hair. The present studies provide information on the influences of hormones by comparing spontaneous replacement to growth initiated by plucking the hair from resting follicles in gonadectomised, adrenalectomised, hypophy- sectomised, thyroid hormone deficient, diabetic, and intact male and female black rats. The effects of various hormone prepaxations have also been observed in these experimental animals. In the rat, spontaneous growth starts periodically in the belly skin and spreads dorsally as a wave in plucked areas the follicles grow simultaneously. Once a hair follicle becomes active, its cycle of growth is the same r •.gardless of how activity is initiated. In the rat, growth of a hair normally requires