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

42 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS for resting follicles and at a lower dose. In the mouse in which the same follicles may have a resting element with a club hair together witk a growing element with a bulb, depila• ion by X-rays of each of these hairs is independent and characteristic. This indicates that the effect is on the epithelium and not dependent on vasculartry. "EFFECTS OF IONISING RADIATION ON HAIR ROOTS OF THE HUMAN SCALP" EUGEr•E J. VXN SCOTT The direct effect of tonising radiation on hair follicles can be studied by microscopic examination of unstained roots of hairs extracted from the irradiated scalp. Changes in the hair root are detectable as early as two days following irradiation and become progressively more manifest thereafter. These changes are confined to growing hair follicles and consist of a characteristic progressive atrophy of the entire hair bulb, which begins in the matrix portion. At the end of 10-14 days complete disintegration of the bulb occurs, leaving a severely tapered proximal tip of extracted hairs. Such hairs fall out at the end of three weeks. The roots of a proportionately few hairs recover during the first week, assume a structurally normal bulb, and con- tinue to prodace a hair the hair shaft has a smaller diameter in a demar- cared zone which can be identified, as judged by its distance from the bulb, as that portion of hair shaft produced during the time of radiation. Calculation of the percentage of growing hairs demonstrating morphological effects of irradiation may be done by examination of one hundred or more hairs manually extracted from areas of scalp exposed to different doses of radiation. Such examinations, repeated at intervals during the week following irradia- tion, reveal that the percentage of hairs showing changes increases linearly in relation to both time and to the dose of irradiation to which the hair roots were exposed. "CHANGES IN HAIR ROOTS OF THE HUMAN SCALP FOLLOWING THERAPY WITH A FOLIC ACID ANTAGONIST" EUGENE J. VAN SCOTT The loss of scalp hair following amethopterin (Methotrexate), unlike that due to either ionising radiation or systemic diseases, is due to a breakage of the hair shaft and not to a falling out "by the roots." Microscopic examination of unstained roots of hairs pulled from the scalps of patients receiving therapeutic doses of amethopterin reveals a transient but reversible injury to the hair bulb. There is a decrease in the diameter of the hair formed during the time of administration of the drug.