266 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS stearin fatty acids such as oleic acid, palmitic and stearic acid inorganic salts and water. In addition to the immediate local effects determined by the blood and nerve supply, these glands are influenced by other factors, such as ho,rmones, diet, drugs, and emotions. The blood supply to the hair is derived from two sources. There are two plexes of blood vessels--one a superficial plexus in the sub-papillary layer which supplies the upper part of the follicle, and a deeper plexus near the subcutaneous tissue, which supplies the papilla. Therefore, in terms of hair growth, the more important plexus is the deep one which nourishes the papilla. The hair also has a muscle supply, the erector pili, which when it con- tracts, causes an erection of the hair. This muscle is attached from the papillary layer of the dermis to the connective tissue outside the follicle, just below the entrance of the sebaceous gland. When this muscle con- tracts, it draws the follicle into a position more at right angles to the skin surface, causing the hair to stand up. In man, the presence of "goose pimples" on exposure to cold is caused by the contraction of these muscles. Under stress or fear, a similar reaction may occur which may last for a long time after exposure to the stress situation. This was described vi3*idly in soldiers evacuated from Dunkirk in World War II, where the constant stimulation of memories by day and dreams at night caused the hair to be erect continuously for months. The rate of hair growth shows many variables. The rate of growth is generally supposed to be the greatest in young women between the ages of 16 to 24. Many other factors such as season, diet, illness, and con- valescence may affect the rate of growth and there are individual differ- ences even among adjacent follicles. Each hair seems to have its own special duration of life, its own characteristic length and rate of growth. Contrary to popular opinion, cutting, shaving or singeing does not hasten hair growth. The diseases causing hair loss are well described in the many textbooks of dermatology, so we will limit our discussion to the ordinary baldness which seems to occur without any apparent disease process. At present there is no one satisfactory or universally accepted explanation for this type of alopecia. However, much time and effort has been expended to explain the various concepts of this type of hair loss. These explanations in most part are based on careful scientific observations but some are theoretical in nature. The following are not listed in any particular order of validity or importance. One of the interesting explanations for the loss of hair is the increased use of hats in our civilization. Specifically, the factors involved are said to be the presence of tight hat bands which cause a diminution of the blood supply to the scalp. Another aspect is that the wearing of hats causes over-

':: BALDNESS AND SOME CHEMICAL ASPECTS 267 !::)'heating of the scalp, thus causing temperature changes which adversely •i•?'affect the growth of hair. 'Furthermore, it is said the use of head gear has !?lessened the necessity of the hair on the scalp acting as a shock reducing and •rotective agent for the head. There are others who feel that the over- i• heating caused by modern heating systems also has a detrimental effect on ilkhair growth. Of course, there is no apparent reason for the sex difference ii: for the proponents of this theory. Another explanation for lack of hair is that as man has become more •:•'.• civilized and uses his brain increasingly more than his body, the amount of ? aervous energy directed toward the brain has deprived those fibers in- •i? rolve d in hair growth. The intellectual man of the future has often been : depicted as a man with a large expanse of a shiny, gleaming scalp. Ob- i'11 servations have been at variance some saying that the number of bald •: :heads at the opera is proportionately greater than at a prizefight. I have '•no statistics on this subject so it is impossible to determine the caliber of .this audience by the ratio of those with hair to those without. i!:i: An important and complex approach to this problem has been in the i):field of endocrinology. The obvious fact that so many more men are '•:11•iaffticted than women has implicated the male sex hormone, but there is no !i•clear-cut evidence that this hormone is responsible for this condition. In certain individuals, it has been clearly shown that testosterone plays an ...important role in inciting common male baldness, but it is not clear whether the action is directly on the papilla or on the surrounding tissues which ß ii:.alters the function of the papilla. •: Another important substance involved in this situation is fat. There is a great deal of controversy present about fat, for in some publications it is the presence of fat that is thought to be responsible, while in other publica- tions it is the absence of this substance which is thought to be responsible. The atrophy of the fat has been described as causing a pressure ischemia i•.[eading to a decrease in t'he nourishment of the hair papillae, and thus con- tributing to baldness. In another histologic study, there was an apparent relationship between the number of hairs and the age of the individual, and also the amount of infiltration of connective tissue into the fat layer sur- rounding the hair roots. This infiltration may either be the cause of the baldness, or may be the result that accompanies hair loss due to other factors acting directly on the hair roots. Studies of hereditary factors involved in this condition show that there is some influence on common baldness, but again more information is needed. Furthermore, there have been studies in the zoological sphere, where there are indications that baldness is just one of the characteristics we have acquired in our ascent up the mammalian tree. Recently, however, with the development of new techniques, a new approach has been made in the field of chemistry using histochemical