44 Observations on the I'ellow- Fever. 



are contagious : for we learn from history, that the 

 plague, when imported into the temperate climates 

 of Europe, ceases at, or immediately after, the winter 

 solstice ; and we learn from Dr. Fothergill's sixth 

 edition of his Observations on the Malignant Sore- 

 Throat "with Scarlet Eruption, that it becomes epide- 

 mic, in the climate of England, only in the autumnal 

 months ; and Dr. Willan, a physician of the first abi- 

 lities now in London, in his Observations on the Dis- 

 eases of that City, asserts, that the progress, not only 

 of the scarlatina anginosa, but of the small-pox, is 

 checked by the first frost in December. 



Even the measles, according to the declaration of 

 the celebrated Sydenham, requires a particular condi- 

 tion or temperature of the air to render its contagious 

 principle active, in the climate of England, for he 

 had never seen it epidemic, or generally diffused, ex- 

 cepting in the vernal months, and it always ceased in 

 the month of July*. 



It certainly ought not to be thought so very extra- 

 ordinary, that the yellow-fever should originate only 

 in tropical climates, when we consider, that several 

 other diseases, like certain animals, are the products 

 of some climates, and not of others. The spotted 

 pestilence, with glandular swellings, originates in 

 Eg}'pt (and, perhaps, in Smyrna), and nowhere else ; 

 the leprosy originates, with very few exceptions, only 



• See the Medical Works of Thomas Sydenham, M. D., tran- 

 sluted by Swan. 



