A new Theory of Fever. 177 



the coop that very night. In the month of Auguft this care 

 ceafed ; but that period is exactly the time when all birds of 

 prey abandon their young to their own exertions. It may 

 be readily concluded, from this inftance, how much game 

 muft be deftroyed by a pair of thefe owls during the time 

 that they rear their young. This obfervation is applicable 

 to the whole race of owls, in general ; and thefe may be 

 confidered therefore as the moft deftructive of all the birds 

 of prey. As the eatable-birds of the foreft repair chiefly in 

 the night-time to the fields, they are particularly expofed to 

 the acute fight, fmell, and claws of thefe birds of the night ; 

 and even the fwift-footed hare feldom efcapes them. 



XIII. AJhort View of the Mitchillian Theory of Fever, and of 

 Contagious Difeafes in general. 



i^ERTAIN exhalations from mar flies and fwamps, and 

 from collections of putrefying vegetable and animal fub- 

 ftances, induce difeafes attended with -different degrees of 

 malignity, according to circumftances. There is a great fimi- 

 larity at leaft in the difeafes induced by the exhalations 

 from marfhesand from putrefying fubftances : it ought to be 

 fo ; for the noxious quality of the former is in confequence 

 of tbeir containing the latter ; and hence fuch difeafes, 

 though improperly, have been called putrid. 



What is the peculiar fubftance, or what the fubftances in 

 thefe exhalations that caufe what are termed contagious dif- 

 eafes ? What the mode of action ? Animal and many ve- 

 getable fubftances, efpecially thofe which contain gluten, 

 give fimilar products when decompofed by the putrefactive 

 procefs. 



Can hydrogen ga3 be the deleterious product ? No — its 

 •bafe combined with different fubftances makes a great part 

 of our aliment : with carbon it forms fat— with oxygen, 



V r ot. Ill, N water 



