40 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS do not become pigmented with melanin. found in the melanocy/e of human skin. Similar structures have also been , ,' "VASCULARITY AND PATTERNS OF 'GROWTH" A. DuRwxm) and K. M. Dept. of A naton,y, University of Leeds, Leeds 2, Englan#. The blood supply to skin and to hair has been reviewed and variations in the supply to different types of hai•s and to hairs during the phases of growth have been studied, particularly in the rat and the rabbit. In the rat the monotrich has a rich supply from a dense network of capillaries around the lower half of the follicle and the dermal papilla contains capillaries awls have a less dense plexus of capillaries around the follicle and no papillary capillaries the smaller follicles do not possess individual plexuses, nor do they have vascularised papillae. In naturally occurring hair growth waves, as seen in the rat and the rabbit, the wave of hair growth is accompanied by a corresponding intensification of the blood supply which keeps step with the growth or recession of the follicle. These vascular changes have been studied in detail in the animals mentioned. Artificially induced growth of hair by pulling and the associated vascular changes were studied in the rabbit, and again a clear inter-relationship was established between hair growth and the vascularity. Local erythematous and eedematous phenomena occur in the skin following pulling. Pulling single ga•ard hairs in rabbits does not induce regrowth. There is a critical number of fibres (varying with conditions), which must be pulled before regrowth is started immediately. This shows that the act of pulling in itself is insufficient to cause immediate commencement of growth in a single follicle. "}¾IITOTIC ACTIVITY OF THE FOLLICLE" W. S. BULLOUGH and E. B. LAURENCE Dept. of Zoology, Birkbeck College, University of London, London, England. 1. The distribution of mitotic activity in the growing follicle of the adult mouse is described. In the fully grown follicle such activity is confined to the matrix cells of the bulb. 2. Observations in vitro (a) It is shown that, for the development of active mitosis in a hair bulb, adequate supplies of oxygen and of some suitable carbohydrate substrate are essential. In the absence of either, the mitotic activity is powerfully inhibited. (b) Ideal carbohydrate substrates for the support of mitotic activity

ABSTRACTS OF PAPERS ON THE BIOLOGY OF HAIR GROWTH 41 Me glucose, fructose, and pyruvate. The various Krebs cycle intermedi- ates testdd were not efficient in this respect. (c) Any substance which is known to inhibit the process of glycolysis, of the Krebs cycle, or.of the cytochrome system, also inhibits the mitotic activity of hair bulbs. The substance 2: 4 dinitrophenol which is said to inhibit the process of energy transfer has the same effect. (d} All the available evidence, therefore, points to the conclusion that the high mitotic activity of a hair bulb can only be maintained by a high level of energy production in the cells. Therefore, it must be expected that mitotically active hair bulbs will normally absorb large quantities of glucose and oxygen, and this is supported by the observations of Ryder (p. 8) on the rate and uptake of radioactive glucose. 3. Observations in vivo (a) Unlike the surface epidermis the matrix cells of a rapidly growing hair follicle show no signs of any diurnal rhythm. No mitotic depression is seen after 6 hours of forced exercise. (b) In starved mice the mitotic activity of the matrix cells does not become depressed until after about 36 hours when the animals are in a state of collapse, and at that time the addition of glucose is all that is needed to restore the mitotic activity to normal. (c) In full shock induced by the removal of tourniquets or by the injection of ATP the mitotic activity of the matrix cells is almost com- pletely inhibited, but in partial shock, mitotic activity is not greatly affected. In skin taken from fully shocked mice and incubated with glucose, mitotic activity returns to normal almost immediately. "PHYSICAL FACTORS WHICH INFLUENCE THE GROWTH OF HAIR" HERMAN B. CHASE The production of hair might be increased in five ways: (1) initiation of a new growth in a quiescent follicle (2) delay or complete prevention of the quiescent state {3) transformation of a follicle into one having a longer growing and a shorter resting phase (4) production of new follicles or multiple follicles {5) increase in the growth rate of a follicle. The first of these is the only practicable one many physical and chemical agents are effective and initiate a new growth of a quiescent follicle. Almost any agent which can cause sufficient damage to result in moderate epidermal hyper- plasia is effective in initiating growth in a quiescent follicle. X-ray, at a dose of about 1,500 r in either the mouse or tha rabbit, stimulates quiescent follicles to activity plucking of club hairs is the best known method and stimulates follicular activity at once. X-rays cause a depilation of growing follicles sooner than that required