Appendix. 393 



That the contagion of the plague, supposing it to be present in the 

 state o[ fomltes,^ might be rendered innoxious by a temperature be- 

 low that of boiling water, appeared to me not improbable, from the 

 evidence of a fact recorded by various writers; viz. that the plague, 

 in countries where it prevails, ceases as soon as the weather becomes 

 very hot. " Extreme heat," says Dr. Russell in his Natural History 

 of Aleppo, (vol. ii, p. 339,) "seems to check the progress of the dis- 

 temper ', for though the contagion and the mortality increased during 

 the first heats in the beginning of the summer, a few days continu- 

 ance of the hot weather diminished the number of new infections. 

 July is a hotter month than June ; and the season, wherein the plague 

 always ceases at Aleppo, is that in which the heats are most excess- 

 ive." In another part (p. 284) of the same volume. Dr. Russell 

 states the greatest heat at Aleppo in June to have been 96° of Fah- 

 renheit, and that of July 101°, in the shade. 



Arguments, also, derived from chemical reasoning, appeared to me 

 to strengthen the probability that a temperature, raised to no great ex- 

 tent, would suffice for the decomposition of infectious or contagious 

 matter. f Of the nature of contagion we are, it is true, entirely igno- 

 rant. But we are entitled to conclude that it is in no case identical 

 with any one of the simple or compound gases, with which chemistry 

 has made us acquainted, and which are unchanged by a temperature 

 below 212°; because each of those gases has been breathed, many 

 of them very frequently, without exciting a specific disease. The 

 subtile poisons which propagate contagious distempers, being the pro- 

 ducts of organic life and of morbid conditions of the animal body, 

 are, it is probable, of a complex nature, and owe their existence to 

 affinities which are nicely balanced and easily disturbed ; even more 

 easily than those maintaining some of the products of vegetable life, 

 which lose their original properties, and acquire new ones, when ex- 

 posed to temperatures of no great amount. Thus, starch is convfert- 



* Fomites (the plural oi fames, fuel) expresses contagious or infectious matter 

 existing in absorbent substances, such as wool, clothing^ &c. In this state of con- 

 finement, it seems to acquire increased virulence and activity. 



f I use the terms 'infection' and 'contagion' as synonymous, because no sufficient 

 distinction has been established between them. It woi.i!d be unseasonable to enter, 

 in this place, into a disquisition about words; but those who take an interest in the 

 verbal part of the subject, will find an excellent view of it (pointed out to me by my 

 son, Dr. Charles Henry) in the Dictionnaire de Midecine, art. Contagion, vol. v, 

 p. 549. Paris : 1822. 



Vol. XXI.— No. 1. 50 



