failed 1 the ntiack of medical observers to the peculiar nature of intra-tropjca? 

 diseases. The appearance of the yellow fever at Boulam, in 1793; its geoera!- 

 prevalence in most of the West India islands ; and subsequently, its more exten- 

 sive diffusion iu different parts of the United States, have been the means of 

 enlarging the original limits of the cent! overs;*, and have given to the discussion 

 an interest inferior to none among medical inquiries. Pre-eminent among the* 

 etiropear* authors who have entered upon this discussion, may be considered the 

 celebrated dr. Chisholm and dr. Haygavth, whose respective writings on the 

 sualrgnant yellow fever are monuments of the learning and talents of their au- 

 thors, and may be pronounced the most able and satisfactory works in support 

 of the doctrines which they have espoused ; as the writings of our late distin- 

 guished countrymen, doctors Rush, and Miller, may be referred to as containing 

 the best summary of the theories which these authors have embraced. 



Although the specific nature of the matter by which certain diseases are pro- 

 pagated is still imperfectly understood, yet it were idle to deny the existence 

 of contagion ; and it. is certain we have recently ascertained, in no inconsidera- 

 ble degree, the laws by which it is governed. " In the present state of medical 

 knowledge," says the Edinburgh Review, " it would not, we conceive, be at ;:1! 

 more absurd to deny the existence of fever altogether, than to maintain that it 

 is not propagated by contagion." Rwiciv of Dr. Haygarlk's Letter to Dr, 



An attnnipt was nrade by the late dr. Richard Bayley^of New- York, to 

 ^stablLh a distinction between contttgion and infection, and to discriminate iiie 

 disfjrtses arising from these tn-o different sources. (Treatise on the Yfllnw Fever 

 ^]f Nero York, 1795.) This distinction has been adopted by some eurouean phy- 

 sicians, and, among other?, by dr. Joseph Adams, but without the due acknow- 

 ledgment. 



About the year 1797, dr. Mitchill promulgated his ingenious doctrines on the 

 pestilential fluids; and in 1801, dr. Edward Miller made public his Attempt to 

 Deduce a Nomenclature of certain Febrile and Pestilential Diseases from the 

 origin- and nature of their remote cause. Medical Repository, vol. 1 and 7. 



In July, 1C03, ;i new theory on the laws governing the communication of con- 

 t:;>.gious and infectious disease?, was published by dr. Hosack, in a letter address- 

 ed to d'r. Colin Chisholm. (Vide Edin. Mtd. and Surg. Journal, vol. 5.) Dr. 

 }'Tosack admits the distinction proposed by dr. Bayley to approach nearer the 

 truth than any other that had hitherto bf;ui offered, but he does not consider it 



as presenting a view of the whole truth. Those diseases winch are communica- 





 rtlJe from one person to another, and are gci.erally considered of a contagious 01* 



infectious nature, are distributed by dr. IT. into three classes. First, such as 

 i'-e communicated exclusively by contact ; as itch, siphylis, sibbens, laanda o* 



