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the increase of the one is generally attended with a sensible diminution of 

 the other 1 ; lastly, the mucous membrane of the intestinal canal, besides 

 secreting mucus exhales likewise a fluid which increases much in quantity, 

 when the cutaneous perspiration is languid, as is proved by the serous 

 diarrahceas so frequently occasioned by a suppressed perspiration. It 

 must be owned, however, that notwithstanding those analogies of structure 

 and function, in the skin and mucous membranes, there exists perhaps a 

 still more intimate connection between its actions and that of the organs 

 which secrete the urine; it has always been observed, that when this last 

 fluid is scanty, there is a greater cutaneous perspiration, and vice versa. 



If we examine, with a microscope, the naked body, exposed during 

 summer to the rays of a burning sun, it appears surrounded with a cloud 

 of steam, which becomes invisible, at a little distance from the surface. 

 And if the body is placed before a white wall, it is easy to distinguish the 

 shadow of that emanation. We may, likewise, satisfy ourselves of the 

 existence of the cutaneous perspiration, by the following experiment: 

 hold the tip of the finger, at the distance of the twelfth part of an inch 

 from a looking-glass, or any other highly polished surface, its surface will 

 soon be dimmed by a vapour condensed in very small drops, which disap- 

 pear on removing the finger. One may, in this manner, ascertain that the 

 cutaneous perspiration varies in quantity, in different parts of the surface 

 of the body, for, on placing the back of the hand before a looking-glass, 

 the latter will not be covered by vapour. 



No function of the animal economy has been the subject of more in- 

 vestigation, nor has any excited the attention of more accurate and inde- 

 fatigable physicians, than the secretion now under consideration. From 

 the time of Sanctorius, who, in the beginning of the seventeenth century, 

 published in his immortal work, " Medicina station," the result of experi- 

 ments carried on, for thirty years, with a patience which very few will 

 imitate, to that of Lavoisier, who jointly with Seguin, aided by the resour- 

 ces of the improved stateof chemistry, instituted an examination of the in- 

 sensible perspiration, we find engaged in this inquiry, Dodart, who in 

 1668 communicated to the Academy of Sciences, which had been founded 

 but a short time, the result of his observations at Paris, under a climate 

 different from that of Venice, where Sanctorious lived : Keill, Robinson, 

 and Rye, who repeated the same experiments^! England and Ireland : 

 Linnings, who performed his in South Carolina; and several physiolo- 

 gists of no less merit, as Gorter, Hartmann, Arbuthnot, Takenius, Win- 

 slow, Haller, &c. who all aimed at ascertaining, with more precision 

 than had been done by Sanctorius, the variations in the cutaneous per- 

 spiration, according to the climate, the season of the year, the age, the 

 sex, the state of health, or disease, the hour of the day, and the quantity 

 of other secretions. 



According toSanctorius, of eight pounds of solid and liquid aliments 

 taken in twenty-four hours, five were carried off by the perspiration, and 

 only three in excrement and urine. Haller conceives this calculation to 

 be exaggerated : Dodart, however, carried it still further, and maintained 

 that the relation of the perspiration to the solid excrements, was as seven 

 to one. 



In France and in temperate climates, the quantity of the cutaneous per- 

 spiration, and of the urine, is nearly the same; it may be estimated at be- 

 tween two and four pounds in the twenty-four hours. We perspire most 

 in summer, and void most urine in winter. The perspiration, like every 



