BACTERIA IN INFECTIOUS DISEASES. 249 



which at the outset would have been fatal in much 

 smaller doses. 



" The immunity which an individual enjoys from any 

 particular disease must be looked upon as a power of 

 resistance possessed by the cellular elements of those 

 tissues of his body which would yield to the influence 

 of the poison in the case of an unprotected person. . . . 

 The resistance of living matter to certain destructive 

 influences is a property depending upon vitality. Thus, 

 living protoplasm resists the action of the bacteria of 

 putrefaction, while dead protoplasm quickly undergoes 

 putrefactive changes." Am. J. of the Med. Sciences, 

 April, 1881,|?. 375. 



The hypothesis of Pasteur would account for 

 the fact that one individual suffers a severe attack 

 and another a mild attack of an infectious disease, 

 after being subjected to the influence of the poison 

 under identical circumstances, by the supposition 

 that the pabulum required for the development of 

 this particular poison is more abundant in the body 

 of one individual than in the other. The expla- 

 nation which seems to us more satisfactory, is that 

 the vital resistance offered by the cellular elements 

 in the bodies of these two individuals was not the 

 same for this poison. It is well known that in 

 conditions of lowered vitality, resulting from star- 

 vation, profuse discharges, or any other cause, the 

 power to resist disease-poisons is greatly dimin- 

 ished, and, consequently, that the susceptibility of 

 the same individual differs at different times. 



From our point of view, the blood, as it is found 

 within the vessels of a living animal, is not simply 



