THE SKIN AS A COMMUNITY OF STRUCTURES ultra-violet treatment brings about these changes is not known. Experiments on systems containing tyrosinase, histochemical investigation and attempts to show a hormone-like action have failed to indicate a positive effect of psoralen solutions or irradiated psoralen solutions on these systems. Unsatur- ated lactones are among the vesicants and have been shown to inhibit certain enzymes containing thiol groups even the lactones, the coumarins, related to psoralen will react with thiol groups. Another lactone which has been reported to have the effect of increasing hair pigmentation is pilocar~ pine (Savill, 1952), an alkaloid which also has known effects on the other epidermal structures, the sweat glands, for example. SOME CONDITIONS AFFECTING BOTH PIGMENT FORMATION AND KERATIN PRODUCTION Like other functions carried out by living tissues, those of pigment formation and keratin production in the normal animal maintain a certain relation to each other. The changes in the skin which take place in the normal cessation of growth of a hair at the end of a growth cycle affect the hair bulb as a unit and cessation of pigment production occurs too. When a part of the coat of a mouse is in the resting phase, plucking the hairs from that area is sufficient stimulus to initiate the changes leading to recon- stitution of an active hair bulb. Both keratin and pigment begin to be produced in step. Where black hairs are formed from a non-pigmented skin, the appearance of black dots on the skin due to pigment formation in the hair bulb indicates that hair growth is taking place although no hair is visible above the surface of the skin. When these mice have their diet markedly reduced in calorific value within a short time of plucking resting hairs, then no appearance of dark spots and no subsequent growth of hair takes place (Loewenthal and Montagna, 1955). Mice have been kept in this condition for two months, a period during which two cycles of hair growth occur on the normally fed mouse, and then the diet has been increased to the normal level. Such an increase in food level results in renewed activity of the hair bulbs in the area plucked two months previously and pigment and keratin formation begin. The phenomena observed in this and other experiments are suggested to be the result of a food-level which is insufficient to produce the energy required for the activity of the hair bulb and maintain the functions essentiM to the life of the animal. If the reduced level of diet was not fed until reconstitution of the hair bulb and growth on the normal diet are well under way, the effect of restricting the food supply is to retard the growth of pigmented hair, but not to prevent it. It would appear that under these conditions local deposits of fat and glycogen laid down in the period on the normal diet are sufficient to provide energy for the activities of the hair bulb during the whole growth-phase. 281

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The effect of one aspect of nutrition on the pigmentation and growth of human hair has been recognised in many areas of Africa where ill-health and disease due to malnutrition exist. This is the condition of"kwashiorkor," which arises in people living on diets deficient in quality and quantity of protein and is observed particularly in infants and young children. One of the features of this disease is a change in the texture and colour of the scalp hair which is finer, softer and straighter and the pigment has a marked red colour in contrast with the normal jet black. Examination of the histology of the scalp including hair bulbs, follicles and shafts has shown these to be of normal structure (Berte, 1954). It was considered possible that the hair bulbs showed an inability to produce normal pigment and keratin because of an inadequate supply of amino acids. Investigation of the amino acid composition of a staple foodstuff of some of these people showed that only small amounts of the sulphur-con- raining amino acids, methionine and cystinc, were present and consideration of the change in amino acid composition of the diet, arising in the weaning of an infant from breast milk to such a diet, revealed a marked fall in the supply of these amino acids. The amino acid composition of the hair in cases of kwashiorkor has been compared with the composition of hair from a normal individual, and in one case hair grown during a period of the disease has been compared with hair grown on the same scalp after the subject had been receiving an adequate diet (Bigwood, 1954 Bigwood and Robbia, 1955). The total sulphur and the cystinc contents of the hair grown during a period of under-nutrition were lower than the contents of these substances in normal hair. The amino acid analyses available do not allow any conclusions to be drawn about whether this is the only change in composition, but it would appear to be the most outstanding. The effects on the hair observed in kwashiorkor can be observed in black-hooded rats by feeding the local diet of Gambia, where the disease occurs, but experiments on the supplementation of this diet by a protein such as casein plus cystinc indicate that this supplementation does not restore the normal condition which is readily obtained by addition of skimmed milk powder. The change in pigmentation and hair growth is not due to a simple lack of sulphur-contain- ing amino acids, but seems related to an adequate supply in a certain form, for example, in a balanced supply of other amino acids. Investigation of the pigment is limited by the methods at present available for examining the melanins. The pigment in the red hair of kwashiorkor behaves differently on a chromatographic column from the pigment of normal, black, African hair and from that of auburn European hair. How- ever, pigments with a similar behaviour to that from kwashiorkor hair can be obtained from normal hair treated with hydrogen peroxide or exposed to ultra-violet light, that is hair in which the pigment has undergone some oxidation (Nagchaudhuri and Platt, 1954). 282