FEVERS. 543 



The substances thus imbued with an active and infectious 

 matter, may be called Fomites ; and it appears to me prob- 

 able, that contagions, as they arise from fomites, are more 

 powerful than as they arise immediately from the human body. 

 " For the facts in proof of all this, which are now commonly 

 known, I refer you particularly to Dr. Lind." 



LXXXIII. Miasmata are next to be considered. These 

 may arise from various sources, and be of different kinds ; but 

 we know little of their variety or of their several effects. We 

 know with certainty only one species of miasma which can be 

 considered as the cause of fever ; and, from the universality of 

 this, it may be doubted if there be any other. 



LXXXIV. The miasma, so universally the cause of fever, 

 is that which arises from marshes or moist ground, acted upon 

 by heat. So many observations have now been made with re- 

 spect to this, in so many different regions of the earth, that 

 there is neither any doubt of its being in general a cause of 

 fevers, nor of its being very universally the cause of intermit- 

 tent fevers, in all their different forms. The similarity of the 

 climate, season, and soil, in the different countries in which the 

 intermittents arise, and the similarity of the diseases, though 

 arising in different regions, concur in proving, that there is one 

 common cause of these diseases, and that this is the marsh 

 miasma. 



What is the particular nature of this miasma, we know not ; 

 nor do we certainly know whether or not it differs in kind : but 

 it is probable that it does not ; and that it varies only in the 

 degree of its power, or perhaps as to its quantity, in a given 

 space. 



" But it seems to be always a combination of moisture and 

 heat which operates here, for the same moisture in cold seasons 

 and cold climates has not the same effects, as is evident when 

 we recede from the equator to the pole ; nor is it occasioned by 

 heat alone, for in the warmest climates, and in the warmest sea- 

 sons of other climates, if they are dry, these fevers are not pro- 

 duced. It is upon this fact that Dr. Lind grounds his whole 

 practice of preserving the health of Europeans in hot climates. 

 But neither does the fever arise when the heat acts upon a pure 

 moisture, such as that of a lake or of the sea, where the exhal- 



