MORE TRUTH ABOUT ODOUR washing. Feet are sometimes decorated by drawing patterns on them with saffron powder. The soles of the feet and the palms are often brushed with fine sand to make them whiter. Another common feature of South India is the chewing of pan leaves, these being usually taken with betel-nuts and slaked lime (with flavoured and scented tobacco). The value of the pan leaves is claimed to be four-fold: 1. It gives a similar effect to lipstick as it dyes the mouth and lips. 2. It acts as a deodorant, possibly due to the chlorophyll in the leaves. $. It aids in strengthening the gums. 4. It supplies calcium---from the lime used. Whatever the veracity of these claims, this habit of chewing is as predominant in India as a whole as is the chewing of spearmint gum in the United States. It is appreciated that the fringe only of the subject has been here touched upon, but it is hoped that some of the cosmetic habits of the East described above will have proved novel to Western readers. MORE TRUTH ABOUT ODOUR By WILLIAM McCARTNEY, Pi•.D., F.R.I.C. "Le probl•me de l'odeur est un probl•me particuli•rement irritant pour un esprit scientifique. •1 l'imprdcision du vocabulaire, s'ajoute le manque de bases solides et d'expdriences positives. Les donndes pr•cises sont encore tr•s rares. On ne saurait s'en dtonner, etant donnd la difficultd du sujet." BORNAND and MARTINET. IT IS said that Kohlrausch, the eminent German scientist, once remarked of Michael Faraday, "Er riecht die Wahrheit' ("He smells the truth"). The renowned English natural philosopher apparently never studied sensory physiology, but had he been alive to-day, what service to knowledge could he not have rendered by "smelling" the truth about olfaction ! For, indeed, we still remain very ignorant and, as Sparhawk reminded us a few years ago, we must not cease to enquire, "What's the truth about odour ?" (Perf. Ess. Oil Rec., 1945, 36, 187-190). Since established facts are not numerous, there has quite rightly been considerable speculation. If much of this has been unfruitful, however, the reason is, perhaps, because it has not been well grounded on results previously attained. And this failure to lay a foundation, in turn, occurs because, all too frequently, such results are unknown to those who express. opinions, make statements, or conduct experiments. 207'

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The purpose of the present communication is to review some publications relevant to some popular ideas about olfaction and which, it seems clear, are little known or, at least, seldom read. Loss oF WEIGHT BY MUSK It has been known for a very long time that a minute quantity of musk can perfume a large space for many years and supporters of radiation theories of olfaction have consequently suggested that the material emits its aroma without losing weight. Now, on at least two occasions, experiments on the evaporation of solid musk have been conducted and it cannot be claimed that they provide any support for this view. The first of these investigations, carried out by John Aitken and published in the Proceedings of the Royal Society of Edinburgh (1905-6, 25, 894-902), is entitled "Evapora- tion of Musk and Other Odorous Substances." Aitken was concerned to show that the odorous particles emitted by musk are in the form of gas or vapour and not, as some had suggested, in the solid form. He drew filtered air over musk (presumably natural musk) into a flask containing a little water. When the pressure of air in the flask was then reduced by applying suction, no cloudy condensation occurred although such condensation was always observed when solid particles (dust) were present. In confirmation of this, Aitken also showed that the odorous material emitted by the musk was not trapped by passage through a plug of cotton-wool. "Loss of Weight of Musk in a Current of Dry Air" is the title of the second investigation which was carried out in 1912-13 by Bazzoni, whose account of the work appeared in the Journal of the Franklin Institute (1915, 180, 463- 469). Using a sensitive micro-balance of special design, he determined the weight of a dried specimen in a current of dry air at intervals during a period of seven months and readily showed that, during this period, a loss of 14 per cent occurred (0.18941 rag. from 1'32245 mg.). Natural musk, of course, is a complex mixture and hence the loss is due to evaporation of volatile matter all of which is not necessarily odorous. PSYCHOGA•.VANIC MEASUREMENT Since nervous emotion is accompanied by changes in the electrical con- ductance of the skin, it has been suggested that the measure of the extent of such alterations might also be a measure of odorous strength and of the degree of pleasure or displeasure aroused in man by odours. About thirty years ago, Auld set out to test this suggestion, but without success (J. Inst. Petrol. Technol., 1923, 9, 889-391). The slight differences in the odours of the petroleum products which he studied were found difficult to record on his "emotion meter" (a simple electrical device incorporating a galvanometer) and when he increased the sensitivity of his instrument, outside influences became so marked that the whole procedure became useless. 208