CLASS II. t. 3. OF SENSATION. igj 



coagulates ; and is faid to be diflblved, and is by fome fuppofed 

 to be in a (late of actual putrefaction. See Sect. XXXIII. I. 

 3. where the truth of this idea is controverted. But in the fe- 

 vers of both this genus and the preceding one, great heat is pro- 

 duced from the chemical combinations in the iecretions of new 

 veflels and fluids, and pain or uneafmefs from the diftention of 

 the old ones - y till towards the termination of the difeafe fenfa- 

 tion ceafes, as well as irritation, with the mortification of the 

 affected parts, and the death of the patient. 



Dyfenteria, as well as tonfiliitis and aphtha, are enumerated 

 amongft the difeafes of external membranes, becaufe they are 

 expofed either to the atmofpheric air, which is breathed and 

 fwallowed with our food and faliva ; or they are expofed to the 

 inflammable air, or hydrogen, which is generated in the intef- 

 tines ; both which contribute to produce or promote the conta- 

 gious quality of thefe fluids ; as mentioned in Clafs II. i . 6. 



It is not fpeaking accurate language, if we fay, that, in the 

 difeafes of this genus the fever is contagious ; fmce it is the ma- 

 terial produced by the external membranes which is contagious, 

 after it has been expofed to air ; while the fever is the confe- 

 quence of this contagious matter, and not the caufe of it. As 

 appears from the inoculated fm all-pox, in which the fever does 

 not commence, till after fuppuration has taken place in the in- 

 oculated arm, and from the difeafes of the fifth genus of this 

 order, where contagion exifts without fever. See Clafs II. i. 

 5. and II. i. 3. 1 8. 



The exiftence of contagious miafmata in the atmofphere was 

 believed even in the time of Homer, and was allegorized under 

 the title of the arrows of Apollo. See catarrhus contagiofus, 

 II. i. 3. 6. Of thefe it is probable, that fome contagious mat- 

 ters are only cliffufed in the atmofphere, as that of the fmall- 

 pox, as it feems only to infect thofe who are very near the va- 

 riolous patient ; and feems to be fwallowed with the faliva, and 

 thence to affect the tonfils. Other contagions may be diffolved 

 in the atmofphere, as that of the meafles, and of epidemic ca- 

 tarrhs, which therefore firft affect the membranes of the noftrils 

 in men, and of the maxillary fmufes alfo in dogs and horfes. 



Contagious materials have been alfo believed from remote 

 antiquity to lodge in the walls of rooms where the fick have 

 been confined ; as in the wards of hofpitals, jails, {hips, as well 

 as in the bedding or clothes of the infected. The methods of 

 purifying infected houfes feem alfo to have been ftudied in the 

 remote times ; the Levitical law directs the walls of the houfe 

 of a leprous perfon to be fcraped ; and in. modern times white- 



waftiings 



