CUTICLE, cuticula, in anatomy, a thin membrane, closely lying upon the skin or cutis, of which it seems a part, and to which it adheres very firmly, being assisted by the intervention of the corpus reticulare.
CUM, the skin, in anatomy, is that strong covering which envelopes the whole external surface of animals. It is composed chiefly of a thin white elastic layer on the outside, called the epidermis or cuticle, and a thicker layer, composed of fibres thickly interwoven, and dispos ed in different directions, which is the cutis or real skin. The epidermis is that part of the skin which is raised-in blisters. This is readily separated from the cutis by maceration in hot_ water. It is very elastic, and in soluble in water and alcohol. Pure fixed alkalies and lime dissolve it entirely. Mr. Hatchett, from many ex periments, has shewn that the epidermis resembles albumen in many of its pro perties, or rather that it is nothing more than a peculiar modification of coagulated albumen. The cutis is a thick dense membrane, composed of fibres inter woven like the texture of a hat. When it is macerated some hours in water, and agitation and pressure are employed to accelerate the effect, the blood, and all the extraneous matter with which it was loaded, are separated from it, but its tex ture remains unaltered. On evaporating the water employed, a small quantity of gelatine may be obtained. No subse quent maceration in cold water has any farther effect. When distilled, it yields the same products as fibrin. The con centrated alkalies dissolve it, converting it into oil and ammonia. Weak acids soften it, render it transparent, and at last dissolve it. Nitric acid converts it into oxalic acid and fat, while, at the same time, azotic gas and prussic acid are emitted. When heated, it contracts,
and then swells, exhales a fetid odour, and leaves a dense charcoal, difficult to incinerate. By spontaneous decomposi tion in water or moist earth, it is convert ed into a fatty matter, and into ammonia, which compose a kind of soap. When allowed to remain long in water, it softens and putrefies, being converted into a kind of jelly. When long boiled in water, it be comes gelatinous, and dissolves com pletely, constituting a viscid Liquor, which, by proper evaporation, is convert into glue. Hence the cutis of animals is commonly employed in the manufac ture ofglue.
From these facts, the cutis appears to be a peculiar modification of gelatine, enabled to resist the action of water, partly by the compactness of its texture, and partly by the viscidity of the gelatine of which it is formed ; for those skins which dissolve most readily in boiling water afford the worst glue. The skin of the eel is very flexible, and affords very readily a great proportion of gela tine. The skin of the shark also readily yields abundance of gelatine ; and the same remark applies to the skins of the hare, rabbit, calf, and ox; the difficulty of obtaining the glue, and its goodness, always increasing with the toughness of the hide. The hide of the rhinoceros, which is exceedingly strong and tough, far surpasses the rest in the difficulty of solution, and in the goodness of its glue. When skins are boiled, they gradually swell and assume the appearance of horn ; then they dissolve slowly.