POPULAR ERRORS. 83 



general, and into those which are particular or personal. Those of a 

 general kind relate to the notions entertained by whole communities, 

 on the nature of the cause or causes which generate typhus and some 

 other fonns of fever, and on th& means which are demanded to pre- 

 vent their occurrence ; and which unhappily consist too often of those 

 measures by quarantine, and fruitless fumigations, which, as substi- 

 tutes for the true means of prevention, occasion the neglect of them. 

 In considering tliis subject it would be my object to shew, that all the 

 fonns of continued, and remittent fevers, owe their origin to the pre- 

 sence of a malaria of a specific nature, and derived from the decom- 

 position of the animal and vegetable matter collected in house drains, 

 and swamps, &c., and other analogous localities ; and whether it be 

 the typhus of European countries, or the yellow fever of America, or 

 the jungle fever of India, or the plague of Egypt, or the malignant 

 cholera of India — they all owe their origin to the malaria generated 

 on the spot where they prevail, and can only become infectious by a 

 multitudinous gathering of the sick into ill-ventilated apartments. 

 The subject is one of great interest, and involves in it the considera- 

 tion of those quarantine regulations which are a standing reproach to 

 the commonwealth of Europe. The subject, however, is too ample 

 to be treated in connection with others, and I shall leave it for a 

 future occasion, and shall now proceed to that branch of my subject 

 of a more personal nature, and perhaps it may be thought more im- 

 mediately affecting ourselves. Of the errors which we may now pro- 

 ceed to notice, few have occupied a larger share of the public mind* 

 or maintained a firmer hold on it, than the opinion that the blood is 

 subject to impurity — that certain gioss or peccant humours are 

 generated in it ; and that these supposed conditions of the blood 

 become the causes of various diseases; and especially of those 

 accompanied by an eruption on the surface of tlie body. The notion 

 is one that has descended from antiquity, and down to a comparatively 

 recent period, was universally taught and believed. It owed, however, 

 its parentage, as well as its permanency, to ignorance, resting for its 

 support on tlie loose analogy of vinous fennentation, so familiar to 

 man in all ages, in which new products are generated with heat, and 

 where the heat evolved in the process was assumed to be imitated by 

 the fever, which precedes or accompanies one class of eruptive com- 

 plaints. These notions, however, with all the incongruities pertaining 



