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transpiration, skin and experiments

PERSPIRATION, in medicine, the eva cuation of the juices of the body through the pores of the skin. Perspiration is distinguished into sensible and insensible. See PHYSIOLOGY.

The skin of man and of animals is pierc ed with an influitude of pores, through which, by means of the transpiration, the parts of the aliments escape which do not contribute to nourishment. Independent ly of the sensible perspiration, which is called sweat, and which is accidental, there is, moreover, one that is insensible, acting more or less at every instant, and which none could conceive to be so abun dant as it is, before the experiments of Sanctorius. This celebrated philosopher had the resolution to pass a part of his life in a balance, wherein he weighed himself, in order to determine the loss oc casioned by the effects of the insensible perspiration. lie has found that this kind of evacuation causes us to lose, in the space of twenty-four hours, :About five eighths of the nutriment which we have taken. Dodard, in repeating afterwards the same experiments, bas had regard to the difference of age, and is convinced that a person perspires much the most in his youth. But the philosophers who have

directed their attention to this object, have not sufficiently distinguished the ef fect of the perspiration or transpiration which is performed by the lungs, and of which the matter escapes by expiration, from the effect which is attributable to the cutaneous perspiration, or to that which obtains through the intermediation of the skin. Seguin has undertaken, in conjunction with Lavoisier, to determine these two effects separately ; and ;after having sought, in the usual manner, the total result of the transpiration, has sup pressed that which is performed by the skin, by applying upon that organ a cover impermeable to the humour which it transmits outwardly : thus has been ob tained the quantity of the pulmonary transpiration : and the mean between the results of these experiments gives seven elevenths for the ratio between this quan tity and that of the cutaneous perspira tion ; that is, the effect produced by the pulmonary transpiration is more than the third of the total effect.