542 PRACTICE OF PHYSIC. 



contagious exanthemata or profluvia is hardly greater than the 

 number of species enumerated in the systems of nosology. 



LXXX. If, while the contagious exanthemata and profluvia 

 are thus limited, we should suppose the contagious pyrexiae to 

 be still of great and unlimited variety, it must be with respect 

 to the genera and species of continued fevers. But if I be 

 right in limiting, as I have done, the genera of these fevers 

 (LXVII. LXX.), it will appear likely that the contagions 

 which produce them are not of great variety ; and this will be 

 much confirmed, if we can render it probable that there is one 

 principal, perhaps one common source of such contagions. 



LXXXI. To this purpose it is now well known, that the 

 effluvia constantly arising from the living human body, if long 

 retained in the same place, without being diffused in the atmos- 

 phere, acquire a singular virulence ; and, in that state, being 

 applied to the bodies of men, become the cause of a fever which 

 is highly contagious. 



The existence of such a cause is fully proved by the late 

 observations on jail and hospital fevers : and that the same vir- 

 ulent matter may be produced in many other places, must be 

 sufficiently obvious. And it is probable that the contagion 

 arising in this manner, is not, like many other contagions, per- 

 manent and constantly existing, but that, in the circumstances 

 mentioned, it is occasionally generated. At the same time, the 

 nature of the fevers from thence upon different occasions aris- 

 ing, renders it probable that the virulent state of human efflu- 

 via is the common cause of them, as they differ only in a state 

 of their symptoms ; which may be imputed to the circumstances 

 of season, climate, &c. concurring with the contagion, and mo- 

 difying its force. 



LXXXI I. With respect to these contagions, though we 

 have spoken of them as of a matter floating in the atmosphere, 

 it is proper to observe, that they are never found to act but 

 when they are near to the sources from whence they arise ; that 

 is, either near to the bodies of men, from which they imme- 

 diately issue ; or near to some substances which, as having been 

 near to the bodies of men, are imbued with their effluvia, and 

 in which substances these effluvia are sometimes retained in an 

 active state for a very long time. 



