FIRST INTERNATIONAL SYMPOSIUM 401 I the intracellular formation of keratin fibrils in those cells destined to form the hair shaft, and showed how such fibrils ultimately filled the dying cells. Those cells destined to be part of the inner root sheath first lay down trich- ohyaline granules which apparently join together and become fibrous in the region where the sheath itself becomes birefringent. In the more static cells of the outer root sheath the cell membranes were shown to be highly folded. Later discussion ranged over the question as to how far the details described might be artefacts due to the drastic nature of the technique, but Dr. Mer- cer was confident that his results were reasonably accurate. The day then ended with a detailed account by Dr. G. Matoltsy (New York) of the chemistry of the keratinization of skin, horn, and especially hair. The second day began with a description by Dr. E. H. Mercer of the bio- synthesis of fibers. This was an especially interesting contribution, in that comparisons were made with such other forms of fiber formation as are seen in collagen, in the silk glands of caterpillars and in the egg-capsule glands of cockroaches. He traced fiber formation from the aminoacid micromole- cules, through the precursor macromolecules to the fibrillar macromole- cules and the stabilized intracellular aggregations of fibrils. He discussed the alternative possibilities that in fibril formation the polypeptide chains of the precursor macromolecules may open out, or that these macro molecular blocks may fuse together end to end. On the latter alternative, if the blocks, are symmetrical a straight fibril should result, but if they are asym- metrical the result should be a helix. After this address, Dr. T. Fitzpatrick (Portland, Ore.) considered the nature of hair pigments. He pointed out that they fall into two chemical groups, the brown-black melanin pigments which are so widespread in Nature and the yellow-red pheomelanin pig- ments. These two pigment groups are under separate genetic control, and the two metabolic pathways and their interconnections were described in detail. Dr. H. Chase (Providence) returned to the question of the various sheaths of cells which form the hair and the inner root sheath. He stressed again the precise way in which the undifferentiated matrix cells orient themselves to form these sheaths, and described elegant experiments by which the matrix cells could be displaced. In those follicles which survived this drastic treatment it was found that the displacement of the matrix cells in no way affected the subsequent formation of the hair, thus showing that the cells are equipotent and that their subsequent differentiation is entirely dependent on the position in which they find themselves. Dr. Chase also introduced the subject of the behavior of the pigment cells, and this was taken up in more detail in the subsequent paper by Dr. M. S.C. Bitbeck (London). Using electron microscopy, he described the structure of the melanocytes on the top of the dermal papilla, gave details of the for- mation of melanin granules in association with intracellular cytoplasmic

402 JOURNAL OF THE SOCIE'IY OF COSMETIC CHEMISTS lamelira, and showed how the granules are passed through the cell wall into the adjacent precortical cells. The attention of the symposium then turned to the physiological aspects of hair formation. Prof. A. Durward (Leeds) began with a stimulating account of the vascularization of follicles. The smaller follicles have no particular blood supply, and capillaries do not even penetrate into the der- mal papillin. The larger follicles, however, are intimately surrounded by a capillary network and their dermal papilla• are well vascularized. In the rat the production of new hairs occurs in waves passing ventrodorsally, and the blood flow was shown to be augmented in regions of rapid hair growth. The paper ended with a consideration of the effects of plucking quiescent hairs. Such treatment activates the follicles, increases the blood flow, and results in the production of new hairs. However, this only happens if a large enough area of hair is plucked, a result which suggests that the pluck- ing of only a few follicles results in too small a stimulus. The second day ended with a paper by Prof. W. S. Bullough and Dr. Edna B. Laurence (Birkbeck College, London) on the mitotic activity of the follicle. They began with a description of the mitotic pattern in the growing follicle, and of the remarkably high rate of mitosis of the matrix cells. The energy relations of this great mitotic activity were then de- scribed, and it was shown by means of in vitro studies that cell division is completely dependent on respiration and that it cannot be supported by glycolysis alone. The two most important raw materials are glucose and oxygen and any inhibitor of glycolysis, the Krebs cycle, the cytochrome system, or the processes of energy transfer immediately inhibits mitosis. In the intact mouse the active mitosis of the matrix continues unabated in almost all circumstances and is only reduced at the point of death through starvation or shock. The final day of the symposium began with another paper by Dr. Chase, who discussed the possible ways in which a resting follicle may be stimu- lated to begin a new phase of growth, and who confirmed the point made by Prof. Durward that a certain minimum number of hairs must be plucked before new growth will commence. He added the important information that in early telogen many more hairs must be plucked to stimulate growth than is necessary in late telogen, a result which suggests the possibility of a slow build-up of some natural stimulator during telogen. He then referred to the effects of radiation, and this subject was taken up in detail by Dr. Van Scott, who described a method of using hair roots as a tool for checking the effects of ionizing radiations on the body. The nutritional problems of the growing hair were next discussed by Dr. M. L. Ryder (Wool Industries Research Association, Leeds) with special reference to wool. Carbohydrate and protein, but not fat, are evidently critically important, and Dr. Ryder went on to describe the results ofexperi-