H&MOLYSINS. 7 



Artificial Immunity against Bacteria Bacteriolytic 

 Power of Serum. This specifically increased solvent 

 action for foreign corpuscular elements on the 

 part of sera of animals previously treated with 

 the same, could not fail to be of the great- 

 est interest to bacteriologists; for a most surpris- 

 ing similarity showed itself between this and the 

 well-known facts of artificial immunity against 

 bacteria as they had been developed by R. Pfeiffer. 

 In order to make this clear to the reader, I must 

 dwell for a moment on this subject of artificial 

 immunity against bacteria for example, against 

 living cholera bacteria. A normal guinea-pig is able 

 to kill and dissolve a number of living cholera 

 bacilli if these be injected intraperitoneally. The 

 freshly drawn serum of the animal possesses the 

 same power. If this serum be heated to 55 C., 

 or if serurn be used that has stood for some time 

 (eight to ten days), this property will have been 

 lost. This power of normal serum and other body 

 juices of the living animal to dissolve appreciable 

 quantities of many bacteria, Buchner, as already 

 stated, ascribed to certain constituents of normal 

 serum which he called alexins. 



These alexins are of very delicate constitution, 

 decomposing when heated to 55 C., or spontane- 

 ously when kept outside of the animal body. If 

 we inject into a guinea-pig a very minute not fatal 

 dose of cholera bacilli, one which the animal is able 

 by means of its alexins to overcome, and if we then 



