HOSACK ON THE LAWS OF CONTAGION. 219 



faeces, &c. whereas, in the close, dirty, and small rooms of the poor, 

 the whole family, generally, caught the fever. Hence we may conclude, 

 that in well-aired and clean apartments, the air is seldom so fully im- 

 pregnated with the poison as to acquire an infectious quality."* 



The observations of the late Dr. Willan are also in point on this 

 subject. " Formerly," says that accurate observer, " the typhus, with 

 petechias, &c. often occurred in our prisons, and proved fatal to those 

 who were under confinement in close cells, or who lodged in crowded 

 apartments. Mr. Box, surgeon of Newgate, informs me that the fever 

 has been rendered less frequent there, and less virulent, by removing the 

 persons first affected, into airy rooms, or wards, and by a general atten- 

 tion to ventilation, cleanliness, &c. so that, at present, petechias do not 

 appear in more than one case in thirty."! And of three hundred and 

 seventy-nine patients committed into the London House of Recovery, 

 says Dr. T. Bateman, nine only, or about one in forty-two, were affected 

 with petechia?.:}: 



The facts which have been ascertained relative to the communication 

 of yellow fever, furnish no less conclusive evidence that this disease, like 

 those already noticed, is, or is not, generally contagious, depending on 

 the qualities of the air to which it may be communicated. The history 

 of every visitation of this disease, in the United States, establishes this 

 truth. It has not only regularly made its first appearance in our sea-port 

 towns, and in those places where the air is most impure ; at that season of 

 the year, and in those seasons when such impurities acquire their greatest 

 virulence ; in those houses which are most crowded with inhabitants, 

 and where there is the least attention paid to cleanliness ; but, wherever 



* Proceedings of the Board of Health in Manchester. — Letter from Dr. Haygarth to Dr. 

 Percival, p. 8. t Willan on Cutaneous Diseases, p. 469. \ Ibid, 



