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SUMMARY.— An autoradiographic technique for studying skin deposition and localization is described and applied to a study of germicides in surfactants. The method involves the use of unfixed frozen sections exposed to dry emulsion‐coated slides. The radioactive germicides carboxy‐14C‐3,4,4′‐trichlorocarbanilide (TCC) in soap containing non‐soap detergent (NSD) and zinc or zirconium pyridine‐2‐thione‐1‐N‐oxide (PTO) in a shampoo were applied to the skin of guinea‐pigs. Auto‐radiograms of the skins showed that from soap, TGC was deposited on the stratum corneum, around the entrances to hair follicles, and was seen in the epidermis and dermis, but not in the follicles or sebaceous glands. From the NSD, TCC was seen in addition in the follicles and sebaceous glands. In one human subject, TCC from NSD was seen on the corneum, in the epidermis and dermis, hair follicles and sebaceous glands and also in the sweat glands. From the shampoo ZnPTO and ZrPTO were seen in guinea‐pig skin on the corneum and in the follicles but whereas ZrPTO was in the epidermis and dermis, ZnPTO was not. In all vehicles the largest proportion of germicide was deposited on the corneum. ZnPTO was shown to be soluble in sebum and to penetrate from sebum into only the hair follicles of guinea‐pigs. Scintillation counting of sections of guinea‐pig skin treated with TCC, ZnPTO and ZrPTO supported the autoradiographic evidence that most of the germicide remained on the corneum.

Epidermal barrier function in rats was experimentally impaired by two separate means, namely, by rendering the animals deficient in essential fatty acids and by evoking a primary cutaneous irritant response by treating with a solution of sodium laurate. Impaired barrier function was manifested by a greatly increased rate of transepidermal water loss. Application to the skin of sunflower seed oil, which is rich in linoleic acid, rapidly restored to normal the abnormally high rates of transepidermal water loss in both experimental cases, and it was shown with the essential fatty acid-deficient rats that there was a concomitant incorporation of linoleic acid of the sunflower seed oil into epidermal lipids. Cutaneous application of olive oil, which is low in linoleic acid but rich in the non-essential oleic acid, did not influence epidermal barrier function. A close relationship of barrier function and essential fatty acids is indicated.

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It was recognized more than 60 years ago that administration of carbohydrate to fasting animals causes a fall in urinary nitrogen output, whereas the giving of fat does not have a similar effect (see review of literature by Munro, 1951). In confirmation of this difference between the actions of carbohydrate and fat, the giving of glucose to fasting subjects causes a sharp and transient fall in blood amino-acid concentration, which does not occur after the administration of fat (Munro & Thomson, 1953). Thus carbohydrate has some specific action on the protein metabolism of fasting animals, but, despite attempts at elucidation, the mechanism remains obscure (Munro, 195 I).