REPORT OX THE LAWS OF COXTAGIOX. 09 



tions or 'general laws'; not that I consider them as entitled to 

 the weight of settled and invariable principles, but as open to be 

 modified and amended by the results of further experience. 



Lmvs of Contagion. 



I. The animal body, when the seat of certain morbid actions, 

 is known to elaborate within itself poisons, which are capable of 

 imparting to healthy individuals the same diseased condition, 

 and the power of generating similar poisons. These poisons 

 have been called contagions, from contingOywhence, contactus; 

 or INFECTIONS, from inftcio. A distinction between these terms 

 has been attempted by some writers ; but, avoiding etymolo- 

 gical discussions, I shall employ them in that general and po- 

 pular sense, which regards them as synonymous or nearly so. 



II. It is consistent with the testimony of the best observers*, 

 that some contagions (chiefly those of typhus, and its congenera,) 

 may originate in the animal body when exposed to the action 

 of certain external causes. Among these causes are confinement 

 in overheated, close, and ill ventilated places ; scanty or bad 

 food ; intemperance ; excessive fatigue ; long exposure to cold 

 and moisture ', and, among mental influences, the whole train of 

 depressing passions and emotions. It was doubted, however, 

 by Mr. Howard f whether any of these causes singly be ade- 

 quate to the production of contagious fever ; but, though they 

 certainly operate more powerfully in conjunction, there is no 

 reason to disbelieve their separate efficiency. For, 1. The 

 crowding of numbers together without change of air has been 

 known to occasion low fevers of the most formidable type. Out 

 of 146 persons, shut up during a whole night of sultry weather 

 at Calcutta, in a wretched prison called the Black Hole, (a cube 

 with sides of only 18 feet,) not more than twenty- three survived, 

 of whom several were affected with low fevers of a typhoid cha- 

 racter, ending in carbuncular eruptions^. 2. Half a century has 

 scarcely elapsed since our prisons and hospitals were almost 

 constantly the seats of fevers of the worst character§, generated 

 within their walls; and though banished from thence by an 

 improved system of construction and management, yet similar 

 fevers continue to originate in the crowded aijd squalid habita- 

 tions of the abject poor. 3. Even among the lower animals, si- 

 milar effects have been produced by the same causes. During a 



• Fordyce, HaygArth, Currie, Clark, Howard, Ferriar, Willan, &c. 



t On Lazarettos, 4to, p; 231. 



t See Mr. Holwell's interesting Narrative, Annual Register, 17.58, p. 278. 



§ Well described by Dr. Hunter, Medical Transactions, vol. iii. p. 345. 



