3 io DISEASES SECT. XXXIII. 2. 3, 



The heat is occafioned from the increafed fecretions either of 

 mucus, or of the fibres, which produce or elongate the veflels. 

 The red colour is owing to the pellucidity of the newly formed 

 veflels, and as the arterial parts of them are probably formed be- 

 fore their correfpondent venous parts. 



3. Thefe new motions are excited either from the increafed 

 quantity of fenfation in confequence of greater fibrous contrac*- 

 tions, or from increafed fenfibility, that is, from the increafed 

 quantity of fenforial power in the moving organ. Hence they 

 are induced by great external ftimuli, as by wounds, broken 

 bones ; and by acrid or infectious materials ; or by common 

 ftimuli on thofe organs, which have been fome time quiefcent ; 

 as the ufual light of the day inflames the eyes of thofe,who have 

 been confined in dungeons ; and the warmth of a common fire 

 inflames thole, who have been previoufly expofed to much cold. 



But thefe new motions are never generated by that pain, 

 which ariies from defeft of flimulus, as from hunger, thirft, 

 cold, or inanitions, with all thofe pains, which are termed ner- 

 vous. Where thefe pains exift, the motions of the affe&ed part 

 are leflened ; and if inflammation fucceeds, it is in fome diftant 

 parts ; as coughs are caufed by coldnefs and moifture being long 

 applied to the feet ; or it is in confequence of the renewal of the 

 ftimulus, as of heat or food, which excites our organs into 

 ftronger adHon after their temporary quiefcence ; as kibed heels 

 after walking in fnow. 



4. But when thefe new motions of the vafcular rnufcles are 

 exerted with greater violence, and thefe veflels are either elonga- 

 ted too much or too haftily, a new material is fecreted from their 

 extremities, \vhich is of various kinds according to the peculiar 

 animal motions of this new kind of gland, which fecretes it ; 

 fuch is the pus laudable or common matter, the variolus mat- 

 ter, venereal matter, catarrhous matter, and many others. 



5. Thefe matters are the prod u6l of an animal procefs ; they 

 are fecreted or produced from the blood by certain difeafed mo- 

 tions of the extremities of the blood-veflels, and are on that ac- 

 count all of them contagious ; for if a portion of any of thefe 

 is tranfmitted into the circulation, or perhaps only inierted into 

 the fkin, or beneath the cuticle of a healthy perfon, its ftimulus 

 in a certain time produces the fame kind of morbid motions, by 

 which itfelf was produced ; and hence a fimilar kind is genera- 

 ted. See Seft. XXXIX. 6. i. 



6. It is remarkable, that many of thefe contagious matters are 

 capable of producing a fimilar difeafe but once ; as the fmall- 

 pox and meafles ; and I fuppofe this is true of all thofe conta- 

 gious difeafes, which are fpontaneoufly cured by nature in a cer- 

 tain 



