54-6 PRACTICE OF PHYSIC. 



and heat, a sufficient quantity of noxious matter may not be 

 exhaled. In all great cities noxious effluvia arise from many 

 putrescent bodies which we are constantly breathing, and yet 

 we very rarely observe any persons affected with fever by them. 

 But that putrefaction alone does not produce intermittent fever 

 is evident from the case of scavengers, anatomists, the persons 

 concerned about whales, &c. among whom the disease in ques- 

 tion is not commonly produced ; and when putrid effluvia have 

 been the cause of fever, as in the case of anatomists, it is al- 

 ways of the continued kind, and one of the varieties of typhus." 



LXXXVI. To render our doctrine of fever consistent and 

 complete, it is necessary to add here, that those remote causes 

 of fever, human and marsh effluvia, seem to be of a debilitating 

 or sedative quality. They arise from a putrescent matter ; 

 their production is favoured, and their power increased, by cir- 

 cumstances which favour putrefaction, and they often prove 

 putrefactive ferments with respect to the animal fluids. As 

 putrid matter, therefore, is always, with respect to animal bodies, 

 a powerful sedative, so it can hardly be doubted, that human 

 and marsh effluvia are of the same quality ; and it is confirmed 

 by this, that the debility which is always induced, seems to be 

 in proportion to the other marks that appear of the power of 

 those causes. 



LXXXVII. Though we have endeavoured to shew that 

 fevers generally arise from marsh or human effluvia, we cannot, 

 with any certainty, exclude some other remote causes, which are 

 commonly supposed to have at least a share in producing those 

 diseases. And I proceed, therefore, to inquire concerning these 

 causes ; the first of which that merits attention, is the power of 

 cold applied to the human body. 



LXXXVIII. The operation of cold on a living body is so 

 different in different circumstances, as to be of difficult explana- 

 tion ; it is here, therefore, attempted with some diffidence. 



The power of cold may be considered as absolute or rela- 

 tive. 



The absolute power is that by which it can diminish the 

 temperature of the body to which it is applied. And thus, if 

 the natural temperature of the human body is, as we suppose 



