FIRST INTERNATIONAL SYMPOSIUM 399 To summarize all the papers given at this symposium, the British .. scientific magazine, Nature (180, 592, 1957), kindly allowed the JouRs^n to quote verbatim their report which follows. Biology of Hair Growth A symposium on the biology of hair growth, organized by Profi W. Mon- tagna (Providence) and Profi W. S. Bullough (Birkbeck College, London) under the auspices of the British Society for Research on Ageing, was held in London at the Royal College of Surgeons during August 7-9. The sym- posium secretary was Dr. G. Bourne (St. Bartholomew's Hospital Medical College, London). The very large audience from Europe and the United States was welcomed by Sir Francis Fraser (British Postgraduate Medical Federation, London), and introductory addresses were also given by Prof. Montagna and Prof. S. Rothman (Chicago), who both referred to the great advances made during the past decade in our knowledge of the structure and physiology of mammalian skin. The first day was devoted to the structure of the hair and the hair follicle. In the opening address Dr. E. Van Scott (Bethesda) dealt with the anatomy of the human hair follicle, describing in particular the changes which occur with age. He was followed by Prof. Montagna, who discussed the manner in which the undifferentiated matrix cells move upward to arrange them- selves in concentric sheaths prior to their differentiation. Of particular in- terest was his account of the follicular blood system, and of the way in which it is turned inside out as the follicle passes from anagen to catagen. Dr. O. Braun-Falco (Mainz) then described the distribution of enzyme systems as revealed by histochemical techniques, stressing among other things the evident importance of Krebs cycle and cytochrome enzymes in the active matrix. In the discussion following these papers attention was directed to what proved to be two of the recurrent themes of the symposium, the role of the dermal papilla and the nature of the drastic change in the matrix cells during the onset of anagen. It was suggested by several speakers that these two are probably closely interrelated, the initial stimulus to the growth of a new hair developing in the dermal papilla and spreading from there to the matrix cells. Evidently the dermal papilla contains active enzyme sys- tems during the follicular growth phase, but there is an apparent lack of activity during the follicular resting phase. The account of follicular structure was continued by Dr. E. H. Mercer (London). With the use of a new embedding medium which allowed ex- cellent sections to be cut at extreme thinness, he was able to show a beauti- ful series of photographs taken with an electron microscope. He first ex- amined the structure of the undifferentiated matrix cells and the irregular nature of their boundary with the derreal papilla. He then gave details of