ABSTRAGTS OF PAPERS GIVEN AT THE SYMPOSIUM ON THE BIOLOGY OF HAIR GROWTH (LONDON, AUGUST 7th-9th, 1957) INTRODUCTION WILLIAM i•ONTAGNA From the point of view of biology, hair follicles are exciting organs. During the cycles of growth, which in different regions of the body last for days or years, they grow to the fullest extent of their inherent ability, and during the time of quiescence they are dormant. Numerous and inexplicable biological phenomena take place, including cyclical growth, di•erentiation and induction. These phenomena are demonstrated and repeated through each full cycle of growth of a hair generation. The purpose of this symposium is to bring together the various distinguished scientists who have studied the different aspects of the biological problems o• hair growth, These range from considerations of growth to the synthesis and chemistry of the hair fibre. We have deliberately excluded the problems of alopecia and pathology these problems must await future considerations, when we understand more fully the normal events in hair growth. STEPHEN ROTHMAN Dept. of Medicine, University of Chicago, Chicago, Illinois. The pilary system is a perfect microcosmic structure in which we find birth, development, ageing and death, activity and rest, colour i0rmation and decoloration, greasiness and dryness, infection and sterilisation, hyper- trophy and atrophy, benign tumours and malignant ones. Such a com- plexity of functions has attracted the attention of very different groups of scientists, and there is hardly any other field in which the groups of interested people is so heterogeneous as they are in the topic of hair• growth. "ANATOMY OF THE HAIR FOLLICLE" EUGENE J. Va• SCOTT Derrnatology Service, National Cancer Institute, Bethesda 14, Maryland. The hair follicles of various regions of the body have a basic similarity in structure modifications and deviations from this basic pattern serve to identify and differentiate the hair follicles of one region from those of another. The hair follicles of the scalp are large, the roots of growing hairs extend deeply into the corium, and the sebaceous glands vary in size. Hair follicles occur singly or in groups each follicle remains as an individual unit within such a group until the level of the epidermis is reached, at which point the 32

ABSTRACTS OF PAPERS ON THE BIOLOGY OF HAIR GROWTH follicles may merge into a common follicular pore. Hence, ou the surface of the scalp multiple hairs may appear to emerge from a single follicle. The hair follicles of the male beard are comparable in size to those of the scalp, but they tend to occur singly. A distinguishing feature of the follicle is a division of the lumen of the follicular neck into two distinct channels' through one channel traverses the shaft of the hair the other directly connects the excretory duct of the sebaceous gland with the skin surface. Approximately one-half of the hair follicles from the upper back are twin rooted. In such follicles two hair roots, each with, its own sebaceous gland, are conioined at the base of a common follicular neck. Hair shafts emerge to the surface through the common follicular neck and follicular pore. Roots of mechanically extracted hairs may be identified as growing (anagen), involutional (catagen) or resting (telogen) by simple microscopic examination. "THE HISTOLOGY OF THE HUMAN HAIR I•OLLIC[E" WILLIAM MONTAGNA Biology Dept., Brown University, Providence 12, Rhode Island. The growing or proliferative part of a hair follicle is the matrix in the lower part of the bulb. This is composed of indifferent cells whose main function is to proliferate ß the cells move up and synthesise keratin that forms the hair and the inner root sheath. The outer root sheath, once formed at the beginning of the hair growth cycle, remains fairly static. In the upper part of the bulb the indifferent cells that have arisen from the matrix become larger and begin to undergo their characteristic differentiation the inner sheath is interlocked with the hair and must grow at the same rate as the hair. In the upper parts of the bulb, melanocytes synthesise melanin and feed it out 'to the cells that make up the cortex and medulla of the hair the cuticle of the hair and the entire inner sheath remain non-pigmented. At the end of a hair growth cycle the follicle forms a club hair and the bulb is largely destroyed a residual vestige of cells is left behind as the seed for the next generation of cells. ' The quiescent hair follicle 'is totally different from an active follicle. It is much shorter than• an active follicle, and consists of a sac Of epidermal cells around the hair club the sac remains in contact with the dermal papilla by a stalk of inciifferent epidermal cells. The stalk of cells and the cells at the base of the epidermal sac comprise the hair germ from which re-grows a new hair follicle when activity sets in again. Capillary networks are particularly rich around the lower part of active hair follicles. Tufts of capillaries penetrate the dermal papilla and connect- ing branches form a rich plexus around the entire bulb. In the upper two-thirds of the follicles vascularity is scant. The vascular pattern of