ERUPTIVE FEVERS. 155 



probable : for there are innumerable instances of the contagion, 

 arising from a person labouring under the smallpox of the 

 distinct kind, producing the confluent ; and on the contrary. 

 Since the practice of inoculation became frequent, we have 

 known the same variolous matter produce in one person the dis- 

 tinct, and in another the confluent smallpox. It is therefore 

 highly probable, that the difference of the smallpox does not 

 depend upon any difference of the contagion, but upon some 

 difference in the state of the persons to whom it is applied, or in 

 the state of certain circumstances concurring with the applica- 

 tion of the contagion. 



DXCVI. To find out wherein the difference in the state of 

 the persons to whom the contagion of the smallpox is applied 

 consists, I observe, that the difference between the distinct and 

 confluent smallpox consists especially in the number of pustules 

 produced ; which, in the distinct, are generally few ; in the con- 

 fluent, always many. If, therefore, we shall be able to discover 

 what, in the state of different persons, can give occasion to more 

 or fewer pustules, we shall probably be able to account for all 

 the other differences of the distinct and confluent smallpox. 



DXCVII. It is evident, that the contagion of the smallpox 

 is a ferment with respect to the human fluids, and assimilates a 

 great part of them to its own nature ; and it is probable, that 

 the quantity thus assimilated, is, in proportion to the bulk of 

 their several bodies, nearly the same in different persons. This 

 quantity passes again out of the body, partly by insensible per- 

 spiration, and partly by being deposited in pustules ; but if the 

 quantities generated be nearly equal, the quantities passing out 

 of the body by the two ways mentioned are very unequal in dif- 

 ferent persons; and, therefore, if we can explain the causes 

 which determine more to pass by the one way than by the other, 

 we may thereby discover the causes which give occasion to more 

 pustules in one person than in another. 



DXCVIII. The causes which determine more of the vario- 

 lous matter to pass by perspiration, or to form pustules, are 

 probably certain circumstances of the skin, that determine more 

 or less of the variolous matter to stick in it, or to pass freely 

 through it. 



DXCIX. The circumstance of the skin, which seems to de. 



