INFECTION AND IMMUNITY. 595 



not immune, and this is at once followed by an intra- 

 peritoneal injection of serum from an immune animal, 

 almost instantly the peculiar disintegration of the bac- 

 teria, as observed in the peritoneum of the immune ani- 

 mal, can be detected. This latter observation is of 

 the utmost importance in its bearing on Buchner's 

 hypothesis, for we see here a serum from an immune 

 animal that is capable of conferring immunity ; capable, 

 on injection into a susceptible animal, of endowing its 

 fluids with the peculiar disintegrating, germicidal 

 function noted in the peritoneum of the immune ani- 

 mal from which the serurn originated ; quickly loses its 

 bacteriolytic activity outside the body, but the influ- 

 ence of which in the peritoneum of a susceptible ani- 

 mal is to call forth at once this interesting phenomenon. 

 Manifestly the germicidal substance in this case is 

 either generated by the tissues as a result of the specific 

 irritation by a something contained in this serum i. e., 

 in consequence of a reaction on the part of the peritoneal 

 tissues, or possibly those of the entire animal or else it 

 is, as Ehrlich conceives it to be, a complex whose physi- 

 ological activity depends upon the union of at least two 

 essential groups the one present in the serum of the im- 

 mune animal, and the other in the fluids of the normal 

 animal. 



In more recent investigations Pfeiffer, in association 

 with Marx, has found that the bactericidal substances in 

 cholera-immune animals are much more abundant in 

 the blood-building organs spleen, lymphatic glands, 

 and bone-marrow than in either the blood or other 

 tissues. 1 



1 Pfeiffer and Marx : Deutsche med. Wochenschrift, 1898, No. 3. 



