Art. III. 2.1.2. SECERNENTI A. 3 3 



Other drugs have this double effect, and belong either to the 

 clafs of Secernentia or Sorbentia, according to the dole in which 

 they are exhibited. Thus a fmall dofe of alum increafes ab- 

 forption, and induces coftivenefs ; and a large one increafes the 

 fecretions into the inteftinal canal, and becomes cathartic. And 

 this accounts for the conftipation of the belly left after the pur- 

 gative quality of rhubarb ceafes, for it increafes abforption in 

 a fmaller dofe, and fecretion in a greater. Hence when a part 

 of the larger dofe is carried out of the habit by (tools, the fmall 

 quantity which remains induces coftivenefs. Hence rhubarb 

 exhibited in fmall dofes, as two or three grains twice a day, 

 ftrengthens the fyftem by increafing the action of the abforbent 

 veffels, and of the inteftinal canal. 



2. Diaphoretics. The perfpiration is a fecretion from the 

 blood in its pafTage through the capillary veflels, as other fecre- 

 tions are produced in the termination of the arteries in the va- 

 rious glands. After this fecretion the blocd lofes its florid 

 colour, which it regains in its pafTage through the lungs ; which 

 evinces that fomething beiides water is fecreted on the Ikins of 

 animals. 



No ftatical experiments can afcertain the quantity of our per- 

 fpiration ; as a continued abforption of tfye moiiture of the at- 

 mofphere exifts at the fame time both by the cutaneous and pul- 

 monary lymphatic. 



3. Every gland is capable of being excited into greater exer- 

 tions by an appropriated ftimulus applied either by its mixture 

 with the blood immediately to the fecerning veflel, or applied 

 externally to its excretory duet. Thus mercury internally pro- 

 motes an increafed falivation, and pyrethrum externally applied 

 to the excretory ducts of the falival glands. Aloes itimulate 

 the rectum internally mixed with the circulating blood ; and 

 fea-falt by injection externally. Now as the capillaries, which 

 fecrete the perfpirable matter, lie near the furface of the body, 

 the application of external heat acts immediately on their excre- 

 tory ducts, and promotes perfpiration ; internally thofe drugs 

 which poffefs a fragrant effential oil, or fpiritus rector, produce 

 this effect, as the aromatic vegetables, of which the number is 

 very great. 



4. It mult be remembered, that a due quantity of fome 

 aqueous vehicle mud be given to fupport this evacuation ; oth- 

 erwife a burning heat without much vifible fweat mult be the 

 confequence. When the fkin acquires a degree of heat much 

 above ie>8, as appears by Dr. Alexander's experiments, no viii- 

 ble fweat is produced ; which is owing to the great heat of the 

 ikin evaporating it as haftily, as it is fecreted -, and, where the 



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