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to keep all Us parts soft, pliant and fit for motion. 

 Hence, from the greater moisture of the air, we per- 

 spire less in winter than in summer, and in rairty 

 weather than in fair. Live therefore, if possible, in 

 a clean house, and in a pure, dry air. 



This inhalation is very considerable. Dr. Keil 

 found his body to have imbibed in one night eighteen 

 ounces of moisture. And on a sudden change of wea- 

 ther from dry to wet, the inspiration, sometimes ex- 

 ceeds the expiration ; there being absorbent-veins, 

 which accompany the numberless arteries from which 

 the perspiration is discharged. To the matter thus 

 imbibed (not the obstruction of the pores) he ascribes 

 what we term a cold. Sweating cures this, by 

 throwing out the noxious matter which was imbibed 

 before. 



The cutaneous vessels both exhaling and inhaling, 

 are capable of contraction and relaxation, by the 

 power of the nerves. This appears from the effects 

 of the passions, which if joyful, increase the circula- 

 tion, and relax the exhaling vessels. Those passions 

 on the contrary, which are sorrowful, and retard the 

 circulation, contract the exhaling vessels, as appears 

 from the dry ness and corrugation of the skin, like a 

 goose-skin after frights ; and from a diarrhoea caused 

 by fear. But the same affections seem to open the 

 inhaling vessels ; whence the variolous or pestilential 

 contagions are easily contracted by fear. 



The benefits of insensible perspiration are so great, 

 that Jife cannot be preserved without it. And the 

 subtility, equability, and plenty of what we perspire, 

 are the grand symptoms of health. 



But how little do we know even of our own frame ! 

 Jt has hitherto passed as an unquestionable triith,that 

 the samematterwhich passes by insensible perspiration, 

 passing in great quantities, is sweat. Whereas an ii> 

 genious physician, Dr. Rogers, has found by numerous 

 experiments, that a person perspires abundantly Jess, 

 when he sweats, than when he does not ; that one 

 who perspires twenty four-ounces in seven hours sleep, 



