SECT. XXXIII. a. DISEASES OF SENSATION. 467 



if the matter is conceived to circulate for fix or 

 feven days with the blood, without producing dif- 

 order, it ought to be rendered milder, or the blood- 

 yeffels more familiarized to its acrimony. 



It is much eafier to conceive from this docTtrine of 

 affociated or fympathetic motions of diilant parts of 

 the fyftem, how it happens, that the variolous iri- 

 fection can be received but once, as before ex- 

 plained ; than by fuppofing, that a change is ef- 

 fected in the mafs of blood by any kind of ferment- 

 ative procefs. 



The curious circumftance of the two contagion$ 

 of fmall-pox and meafles not adting at the fame 

 time, but one of them reding or fufpending its ac- 

 tion till that pf the other ceafes, may be much 

 eafier explained from fympathetic or aflbciated acti- 

 ons of the infecled part with other parts of the 

 iyitem, than it can. from fuppofing the two conta- 

 gions to enter the circulation. 



The (kin of the face is fubjecl: to more frequent 

 yiciffitudes of heat and cold, from its expofure to 

 the open air, and is in confequence more liable to 

 fenfitive affociation with the ftomach than any ther 

 part of the furface of the body, becaufe their ac- 

 tions have been more frequently thus affociated. 

 Thus in a furfeit from drinking cold water, when 

 a perfon is very hot and fatigued, an eruption is 

 liable to appear on the face in confequence of this 

 fympathy. In the fame manner the rofy eruption on 

 the faces of drunkards more probably arifes from 

 the fympathy of the face with the ftorjiach, rather 

 than between the face and the. liver, as is generally 

 fuppofed. 



This fympathy between the ftomach and the fkin 

 of the face is apparent in the eruption of the fmall- 

 pox ; fmce, where the difeafe is in considerable 

 quantity, the eruption of the face firft fucceeds the 

 ficknefs of the ftomach. In the natural difeafe the 



ftomach 



