ADDITIONAL NOTES ON CONTAGION. 245 



tion of a febrile sort readily assumes the character of the prevailing disorder. We 

 know this to be experienced in the diseases of other countries, and we see it daily exem- 

 plified in our own : both in our cities and in the country towns, when, after heavy showers 

 of rain, and the action of a hot sun, a decomposition of vegetable and animal substances 

 takes place, and dysentery or typhus fever is produced, it assimilates the air to itself, 

 whatever may be the acting poison. But under other circumstances of weather and sea- 

 son, the disease thus originating from some local circumstances, or from a peculiar habit 

 of body in the person so affected, does not extend beyond the family in which it first oc- 

 curred, or, perhaps, the individual in whom it originated. 



This class of diseases, therefore, like the former, has a law peculiar to itself; i. e. the 

 diseases composing it are communicable, or otherwise, depending upon the condition of 

 atmosphere in which they occur or are introduced — whereas those of the second class are 

 conveyed from person to person, through a pure as well as an impure medium : but they 

 also are rendered more virulent and malignant in an atmosphere charged with miasmata 

 than in that which is free from such ingredients. 



It is also, I believe, generally true of the diseases of the third class, not perhaps ex- 

 cepting the plague and yellow fever, that they may be taken a second time. This has 

 been advanced by the advocates for the domestic origin of yellow fever, as an argument 

 against the contagiousness of this disease. 



But, upon the same principle, they must deny the contagiousness of all those disorders 

 which I have enumerated in the first class, as itch, syphilis, &c. ; for most of them are also 

 to be taken a second time : yet they are acknowledged by all to be contagious diseases. 

 In the same manner, many persons make the small pox a standard, and conclude that yel- 

 low fever is not contagious, because it is not communicated under the same circumstances- 

 of atmosphere and season, and governed by the same laws with that disease. 



They might with the same propriety conclude, that the scarlet fever is not contagious, 

 because it is not attended with the pustules of small pox. This teaches us the im- 

 portance of correct language to convey the several degrees of contagion which have been 

 noticed ; and that, while we may make use of the terms now in use, we should annex to 

 them such explanations as will convey those different laws of communication which have 

 been enumerated. With those precautions in the use of the language we employ, I 

 believe, the contagionists and non-contagionists will find themselves very much in the 

 situation of those theologians of whom Pascal speaks, and ready to adopt the expression 

 of one of them, when he observes, 



" La difference qui est entre nous est si subtile, qu'a peine pouvons nous la marquer nous 

 memes." 







