HOSACK ON THE LAWS OF CONTAGION. 215 



But to conclude upon this part of the subject, and in the language of 

 Dr. Chisholm himself, " Every physician who has delivered his opinion 

 of the origin of the plague maintains, that a peculiar state of the air 

 is absolutely necessary to establish the powers of contagion, and give 

 circulation to the imported infection."* 



Another disease which I have placed in the same class with the 

 plague, and have considered as governed by the same laws of commu- 

 nication, is dysentery. By this disease I mean not that local affection of 

 the bowels which is frequently symptomatic of diarrhoea, and unac- 

 companied with fever, but that form of it which has been described by 

 Pringle, Blane, and other practical writers, under the title of epidemic 

 dysentery, or the dysentery of camps. 



This disease, like the plague, appears also to derive much of its infec- 

 tious character from the condition of the atmosphere in which it takes 

 place : in pure air, where cleanliness and ventilation are attended to, it 

 rarely extends beyond the individual in whom it first originates; but in a 

 vitiated atmosphere, loaded with moisture, marsh effluvia, or the perspi- 

 rable matter, and other excretions of the human body, especially where 

 many persons are crowded together and in small apartments, dysentery 

 communicates itself to the greater part of those who may be exposed 

 to its influence. Zimmerman remarks, that " in general it appears to 

 him that dysentery became contagious purely through nastiness and the 

 crowding many people together in a small space, but was by no means 

 so of itself't 



And as a further evidence that the disease was derived not from the 

 noxious qualities of the atmosphere alone, but from contagion communi- 



* F.9say on the Malignant Pestilential Feyer, vol. 1. p. 286. 

 f Zimmerman on Dysentery, p. 20. 



