434 BACTERIOLOGY. 



only after the appearance of considerable elevation of 

 temperature, which lasts for a long time. In explana- 

 tion 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 subjected, and which 

 is necessary before they are in a position to bring about 

 the condition of immunity. They claim that the bac- 

 terial products employed in producing immunity in this 

 case are not, in reality, the immunity-affording substance, 

 but that they are only the agents that bring about in 

 the tissues of the auimal alterations that result in the 

 production of another body that protects 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 this 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 former case the 

 actual protecting body had first to be manufactured by 

 the tissues ; whereas, in the second it is already pre- 

 pared, and is introduced as such into the second animal. 



They found the serum of immunified animals to be not 

 only capable of rendering other animals immune, but that 

 it possessed curative powers when the disease is already 

 in progress. The serum of immunified animals, when 

 injected into the circulation of animals in which there 

 was a body- temperature of from 40. 4 to 41 C., reduced 

 this temperature to normal (37.5 C.) in twelve con- 

 secutive experiments during the first twenty-four hours 

 following its employment. 



In their opinion, the crisis, seen in pneumonia in 



