628 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS fluorescence microscopy I have been particularly impressed by the work of Jarrett on psoriasis, employing U.V. fluorescent microscopy. Normal human skin shows the horny layer devoid of nuclei. In a transverse section of dandruff scale by U.V. fluorescence, yellowish nuclei are clearly seen, as also in a section of psoriatic scale. In this case the upper region of the horny layer tends to be bluish, in contrast to the brick red normal horny layer when stained in the same way. Sellotape stripping of normal skin shows separate horny cells with no visible nucleus. Flakes from the scalp removed by combing when dandruff is not apparent are virtually identical to the Sellotape strippings. A dandruff scale at the same magnification is obviously much larger, with distinct nuclear-staining material persisting. Ethyl oleate-induced scales from the mouse are of similar size to human dandruff scale, the nuclear material again being visible. It is not uncommon in applying irritant substances to animal skin to have reactions such as peeling, weeping and crusting but in the case of ethyl oleate applied as a 70% solution in ethanol the hair becomes filled with discrete, creamy-coloured scales looking much like human dandruff. In the case of mouse skin to which ethyl oleate has been applied, the overall thickness is increased a significant feature is the distance apart of the prickle layer cells (a phenomenon known as spongiosis) which is regarded as typical of an inflammatory condition. Nuclei or their remnants are still apparent throughout most of the depth of the horny layer. In the interfollicular region of mouse-tail skin, the granular layer is not strongly in evidence, but in the perifollicular region there is a pronounced granular layer. After treatment with 12 applications of 1,000 I.U. Vitamin A in petroleum jelly the granular layer is very pronounced, both in the perifollicular and interfollicular regions. This is similar to Jarrett's descrip- tion of the effect of Vitamin A on rat tail. Though omitted from the paper to avoid confusion, applicator tests have been carried out with ordinary nutrient agar, for bacteria on the scalp. A veritable culture collection is obtained with most subjects there is a pre- dominance of micrococci but also a range of other organisms. DISCUSSION DR. R. M^RECH^L: If the presence of unsaturated compounds in sebum lipids may be involved in the causation of dandruff, something should also be said about the influence of excessive androgens in the blood irrigating the scalp. This is one of the most important sources of dandruff after puberty in young men and women, and in women experiencing a decrease in oestrogen through the natural or artificial menopause as well as when pathological androgen appears from the ovaries and suprarenal glands. Dandruff is often present with greasy hair, excess lipid on the scalp and hair being due

Figure 11 T.S. Normal Mouse Skin. Magnification (of original photomicrograph) x 155. Figure 12 T.S. Mouse Skin treated with Ethyl Oleate (showing nucleated horny layer, hypertrophy and spongiosis of prickle-cell layer). Magnification (of original photomicrograph) x 155. Figure 1.• T.S. Human Dandruff Scale (U.V. fluorescence photo- micrograph ). _Magnification (of ori.•inal photomicrograph) x 40