SECT. XX&II. 3. DISEASES OF IRRITATION. 4 sj 



V/hich pafs the cold feafon in a torpid flatc, and 

 which revive on being warmed by the fire. This 

 .neceffary ftimulus of heat has two Iburces ; one from 

 the fluid atmofphere of heat, in which all things 

 are immerfed, and the other from the internal com- 

 binations of the panicles, which form the various 

 fluids, which are produced in the extenfive fyftems 

 of the glands. When either the external heat, 

 which furrounds us, or the internal production of 

 it, becomes lefTened to a certain degree, the pain of 

 cold is perceived. 



This pain of cold is experienced mod fenfibly by 

 pur teeth, when ice is held in the mouth ; or by 

 our whole fyftem after having been previoufly ac- 

 cuftomed to much warmth. It is probable, that this 

 pain does not arife from the mechanical or chemi- 

 cal effects of a deficiency of heat ; but that, like 

 the organs of fenfe by which we perceive hunger 

 and thiift, this fenfe of heat fuffers pain, when the 

 flimulus of its object is wanting to excite the irri- 

 tative motions of the organ ; that is, when the fen- 

 forial power becomes too much accumulated in the 

 quiefcent fibres. See Sect. XII. 5. 3. For as the 

 periilaltic motions of the flomach are leflened, when 

 the pain of hunger is great, fo the action of the 

 cutaneous capillaries are leflened during the pain of 

 cold ; as appears by the palenefs of the fkin, as ex- 

 plained in Sect. XIV. 6. on the production of ideas. 



The pain in the fmall of the back and forehead in 

 the cold fits of the ague, in nervous hemicrania, 

 and in hyfteric paroxyims, when all the irritative 

 motions are much impaired, feems 10 arife from this 

 caufe ; the veflels of thefe membranes or mufcles 

 become torpid by their irritative affociations with 

 other parts of the body, and thence produce lefs of 

 their accullomed fecretions, and in confequence lefs 

 heat is evolved., and they experience the pain oi" 



cold 



