CLASS II. i . 3. OF SENSATION, I g i 



ORDO i. 



Increafed Senfation. 

 GENUS III. 



With the Production of new Veffeh by external Membranes of 

 Glands i with Fever. 



THE difeafes of this genus are perhaps all produ&ive of con- 

 tagious matter , or which becomes fo by its expofure to the air, 

 either through the cuticle, or by immediate contact with it ; 

 fuch are the matters of the fmall-pox and meafles. The puru- 

 lent matter formed on parts covered from the air by thicker 

 membranes or mufcles, as in the preceding genus, does not in- 

 duce fever; and cannot therefore be called contagious ; but it 

 acquires this property of producing fever in a few hours, after 

 the abfcefs has been opened, fo as to admit the air to its furface, 

 and may then be faid to confift of contagious miafmata. This 

 kind of contagious matter only induces fever, but does not pro- 

 duce other matter with properties fimilar to its own ; and in 

 this refpecT: it differs from the contagious miafmata of fmall-pox 

 or meafles, but refembles thofe which have their origin in crowd- 

 ed jails ; for thefe produce fever only, which frequently de- 

 flroys the patient ; but do not produce other matters fimilar to 

 themfelves j as appears from none of thofe who died of the jail- 

 fever, caught at the famous black aflizes at Oxford, at the be- 

 ginning of this century, having infedted their phyficians or at- 

 tendants. 



If indeed the matter has continued fo long as to become pu- 

 trid, and thus to have given out air from a part of it, it acquires 

 the power of producing fever -, in the fame manner as if the ul- 

 cer had been opened, and expofed to the common air ; inftan- 

 ces of which are not unfrequent. B And from thefe circumftan- 

 ces it feems probable, that the matters fecreted by the new veflels 

 formed in all kinds of phlegmons, or puftules, are not conta- 

 gious, till they have acquired fomething from the atmofphere, 

 or from the gas produced by putrefaction ; which will account 

 for fome phenomena in the lues venerea, cancer, and of other 

 contagious fecretions on the fkin without fever, to be mention- 

 ed hereafter. See Clafs II. i. 4. 14. 



The theory of contagion has been perplexed by comparing it 

 with fermenting liquors , but the contagious material is (hewn 

 in Seclion XXXIII. to be produced like other fecreted matters 



by 



