SUMMARY.— The coefficient of friction has been determined for skin and various materials. It has been established that the behaviour of skin is not portrayed by the simple laws of friction, but by a more complex relationship of the type F =μWn. This is probably because skin is subject to viscoelastic rather than purely plastic deformation. Friction may be altered by the type of material in contact with skin and is further influenced by surface lubrication. Dry talcum powder reduces friction slightly for certain materials against skin, but increases friction when it becomes wetted.

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SUMMARY The thickness of the forearm skin and its collagen content and density were measured in a group of patients with acromegaly and hypopituitarism. In acromegaly the total content, thickness and collagen density were all increased. There was a smaller and less consistent increase in percentage collagen content. In hypopituitarism total skin collagen and thickness were both decreased and collagen density and percentage collagen content remained normal.

Summary.— We have examined hairs from psoriatic patients by scanning electron microscopy and compared them with hairs from normal subjects. Micropits were seen in normal hair cuticle cells and in those from psoriatic subjects. Their significance is unknown. Dystrophic changes of these cells are associated with the psoriatic diathesis, occurring significantly more often in hairs from unaffected as well as from affected skin of patients with psoriasis compared with controls. We confirm previous observations that the hairs growing from psoriatic plaques are significantly thinner than those growing elsewhere on psoriatic subjects and than those of normal controls. These studies confirm and expand previous evidence of hair shaft abnormalities in psoriasis.

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