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

34 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS quiescent follicles is quite different. Since the bulb of the active follicles degenerates, the plexus of capillaries around it collapses in a bundle at the base of the dermal papilla. The papilla itself flows away from the tufts of capillaries and comes to rest iminediately above it. Just below the entrance of the sebaceous gland, hair follicles are sur- rounded by a collar of sensory nerves that record pressure stimuli. Oddly enough, these nerves are rich in cholinesterase, like the nerves of t•he para- sympathetic nervous system. These sensory nerves are particularly in evidence around the nerves of the scalp. "THE HISTOCHENIISTRY OF THE HAIR FOLLICLE" OTTO BRAuN-FA•.CO Joh. Gutenberg-Universitlit Hautklinik, Main,, Germany. This paper presents a review of the histochemical findings in human hair follicles. Of the inorganic substances, calcium, magnesium, zinc, copper, sulphates, phosphates and iron have been investigated in quiescent and active hair follicles. The distribution of glycogen, PAS-positive but diastase resistant material and acid mucopolysaccharides in and around hair follicles is different during the different stages of hair growth. These substances are much more abundant in growing than in resting hair follicles. For the first time the histotopography of lipids, and especially that of phospholipids, unsaturated lipids and plasmal, has been reported fully in the different parts of the hair follicle. Amino acids, protein-bound sulphydryl groups and disulphide groups, as well as nucleic acids, have been studied during different stages of hair growth. The histochemical localisation of enzymes in the hair follicles is particularly important. Phosphorylase, succinic dehydrogenase, cytochrome oxiduse, esteruses, acid and alkaline phos- phatases, 5-nucleotidase, glucose-6-phosphatase, cholinesterase,/•-glucuroni- duse, amino-peptidase and carbonic-anhydrase have been studied and an attempt has been made to deduce their functional importance in relation to hair growth. Histochemical studies of hair keratinisation are somewhat hampered by technical limitations of the methods used for the identification of keratin. The histocnemical composition of trichlohyalin and of the keratinisation, the sigrificance of the nuclei in relation to keratinisation, and the fate of the nuclei during keratinisation are discussed. "THE ELECTRON MICROSCOPY OF THE HAIR FOLLICLE" E. H. M•Rc• Chester Beatty Research Institute, Royal Marsden Hospital, London, S.W. 3, England. Thin sections of a variety of kerati•ised tissues, hair, skin, feathers, etc., show that a continuous structureless dermal-epidermal membrane (ca.