HYGIENE IN MANUFACTURING PLANT AND EFFECT ON EMULSIONS 403 enormous bacterial population builds up, which, I know from experience, never gets rid of itself. It is true that one can use formaldehyde in order to disinfect the columns, but then there is the problem of getting rid of the formaldehyde, which I understand is even more difficult than getting rid of the bacteria. You say that the only certain method of destroying bacteria and fungal spores is by autoclaving. I would like to know if there are any fungal spores which will stand more than, say 100øC. THE LECTURER: I believe that there are fungal spores amongst some of the Penicillia which will resist heating to 100øC or more. MR. J. JEFFRIES: It is indeed very important to get rid of whatever one is using to clean up demineralized water, be it formaldehyde or chlorine, as all these compounds can play havoc, for example, with dyes in the finished product. We are in a difficult position in the problem of demineralized water versus distilled water because the former provides us with the only method of producing the volumes of water that we need in a comparatively short time, and there are many occasions when one can use thousands of gallons in a normal working day. One would never obtain this volume of water from a conventional still. MRS. H. BUTLER : I have had the misfortune to produce a food emulsion which is sold through chemists and where it is impossible to use a preservative. Unfor- tunately we got a yeast infection. I think that the only way to make sure that water is sterile is to boil it well for a quarter of an hour just before use. Do you agree with that ? I think that just rinsing is dangerous, because a water rinse which dissolves the water from your emulsion will leave a residue of oil on the surface, where spores can stay. So the rinsing must be combined with cleaning and we found that we had to pump chlorinated water round the system before making any product. Each batch had still to be tested for organisms. THE LECTURER: I sympathize with you for having a yeast infection in your plant. This is a very nasty thing to get rid of. On the other hand, I do not really think that just boiling your water will be sufficient, because you may well have con- taminants in the form of spore bearing organisms. This is one of the reasons why demineralized water is so good, and distilled water even better, provided your resin beds and the lines from your storage tanks to your actual manufacturing plant are kept scrupulously clean. MRS. I-I. BUTLER: We actually boiled the water phase a quarter of an hour. We then added the ingredients of the water phase, we boiled again, and pumped without it being open to the atmosphere the same with the oil phase. For the last four or five years we have been manufacturing under those conditions without any micro-organisms at all. We found that yeast was resistant even to hypochlorite, to heat, and we still had contamination after cooking the oil phase for a quarter of an hour. THE LECTURER: This is very interesting, but it is laborious, very expensive, and time-consuming.

J. Soc. Cosmetic Chemists 16 405-411 (1965) ¸ 1965 Society of Cosmetic Chemists of Great Britain The Sebaceous Glands F. j. EBLING* Based on a lecture delivered before the Society on 25th February 1965. Synopsis--The structure, mode of secretion, distribution and development of the sebaceous glands are reviewed, the composition of sebum is described, and its function is debated. The actions of androgens, oestrogens, and progestogens on the sebaceous glands are discussed. It is concluded that while traditional views of the function of the sebaceous gland may be challengeable, the gland is far from vestigial in structure and, moreover, its sensitivity to male hormones is no less than that of the accessory male sexual organs. For these reasons a functional status for the gland ought to be assumed, though it is possible that this is not yet fully understood. INTRODUCTION The human scalp and face may have as many as 900 sebaceous glands in each sq cm of skin (1). These glands produce a waxy secretion known as sebum, and in adults about 100 •g cm•/hr of lipid material can be removed from the forehead by absorption on pads of cigarette paper (2-4). Thus a single forehead, say 100 cm • in area, produces nearly 2g of sebum in a week. What is sebum ? What is its function ? How it is produced and how is the activity of the sebaceous gland controlled ? STRUCTURE, MODE OF SECRETION, DISTRIBUTION AND DEVELOPMENT OF SEBACEOUS GLANDS The sebaceous gland is holocrine its secretion is formed by complete disintegration of the glandular cells. In man the gland consists of a series of lobes or acini, each connecting to the main sebaceous duct which itself normally opens into the pilary canal (1) in rodents the gland consists only of one or two simple sacs. Sebaceous cells are replaced by cell division at the periphery of the lobes, and the cells differentiate and disintegrate as *Department of Zoology, The University, Sheffield, 10, Yorks. 405