476 BACTERIOLOGY. 



by subjecting it to temperatures somewhat higher than 

 that at which it was produced by the bacteria. The 

 Klemperers found, that if this substance was heated to 

 a temperature of from 41° to 42° C. for three or four 

 days, or to 60° C. for from one to two hours, its intra- 

 venous injection was followed by complete immunity 

 in from three to four days; whereas, if the unwarmed 

 material was used, immunity did not appear before four- 

 teen days, and then only after the employment of rela- 

 tively large amounts. Moreover, when the previously 

 heated products are introduced into the circulation of 

 the animal the systemic reaction is of but short dura- 

 tion; but if the unwarmed substance is employed, immu- 

 nity is manifest only after the appearance of considerable 

 elevation of temperature, which lasts for a long time. 



In explanation of these differences they suggest that, 

 in the latter case, the high fever that is seen to occur in 

 the animal may serve to replace the warming to which 

 the bacterial products had not previously been sub- 

 jected, and which is necessary before they are in a posi- 

 tion to bring about the condition of immunity. They 

 claim that the bacterial products employed to produce 

 immunity in tliis case are not, in reality, the immunity- 

 affording substance, but that they are only the agents 

 that bring about in the tissues of the animal alterations 

 that result in the production of another body that pro- 

 tects the animal. In support of this, their argument is 

 that several days are necessary for the production of 

 immunity by the introduction into the animal of the 

 bacterial products; whereas, if the blood-serum of tliis 

 animal, which is now protected, be introduced into the 

 circulation of another animal, no such delay is seen, 

 but instead, the animal is forthwith protected. In the 



