MILK WHITE APPEARANCE AND ITS SIGNIFICANCE of oil in water results in a tremendous increase of the interfacial area. One c.c. of a fine emulsion with an average particle size of one micron pos- sesses about one thousand billions of droplets with an interracial area of 30,000 cm.• or approximately thirty-two square feet. Since the development of opacity is dependent upon particle size, the importance of the above figures can be imagined. A further advantage of the emulsified system is the possibility of intro- ducing otherwise immiscible hydrophylic and hydrophobic compounds. Cosmetics may contain water-soluble salts, sun screening agents, perfumes and water-insoluble preservatives, etc. The combination of water in oil cosmetic emulsions brings about a greater degree of cleansing action since the aqueous phase will remove the residues of perspiration and water-soluble dirt, whilst the oil phase will remove fatty excretions of the skin and previously applied cosmetics. One should be aware that certain ingredients, including inorganic salts, might be opposed to the stability of an emulsion. A breakdown in the emulsion system will naturally reduce the opacity. In certain cases a minor instability in the system may lead to reversible changes which are known as sedimentation. Below the upward creaming layer or above the downward creaming layer may appear a partial loss in opacity. The creaming layer itself, however, being the accumulation of emulsified particles, remains fully opaque. A major instability in an emulsion which results in irreversible separation will mean considerable reduction in opacity. This is evident since the breaking of the emulsion has destroyed those optical properties which were in the first place responsible for the opacity. For this reason it is necessary that cosmetic emulsions such as deodorant lotions or creams and sun screen preparations neither sediment nor break. CONCLUSIONS Opacity in an emulsion is a function of the refractive indices of the two phases, the ratio of oil and water and the size of the emulsion particles. We have seen that the factors which promote and ensure the stability of emulsions are also responsible for opacity. Opacity may therefore be regarded as a sign of stability and without a doubt lends greatly to the attractive appear- ance of an emulsion. REFERENCES Emulsionen, Dr. E. Manegold. The Theory of Emulsions, W. Clayton. Introduction to Emulsions, G. M. Sutheim. Kohlenzvasserstoj•6l• und Ferry, Prof. Dr. D. Holde.

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