THE LTSINS. 123 



With these facts at his command Pfeiffer ' formulated a theory of 

 bacteriolysis, the chief points of which may be stated as follows : 

 The immunizing substance in cholera serum has but feeble action and 

 is only the antecedent of a substance formed in the peritoneum of 

 the guinea-pig which has a specific solvent action on the vibrios. 

 The immunizing substance in the serum is a stable, relatively inac- 

 tive body which bears a relation to the specific bacteriolytic substance 

 formed in the peritoneum similar to that which glycogen bears to 

 grape-sugar. In case of need, the inactive substance in the serum is 

 transformed through the active agency of the cells of the body into 

 the specific bacteriolytic form. This change can be brought about 

 by the addition of suitable normal serum. In the added serum there 

 is a " something " (Etwas) present in small amount which is able to 

 transform the relatively inactive substance into the active form, but 

 which in vitro is soon used up, while in the animal body this active 

 principle continues to be secreted by the cells of the body as long as 

 they are stimulated by the presence of the cholera bacteria. The 

 active principle is a ferment and bacteriolysis is a fermentative proc- 

 ess in which specific ferments act only on certain cells, just as certain 

 yeasts act only on sugars of certain definite constitution. 



The question of the identity of bacteriolytic and agglutinating sub- 

 stances in the sera of immunized animals became prominent, but 

 Pfeiffer and KoUe^ soon discovered an immune serum which was 

 strongly bacteriolytic but without agglutinating action ; while on the 

 other hand, Frankel and Otto ' found that the blood serum of pup- 

 pies fed upon typhoid cultures had a marked agglutinating effect, but 

 was without bacteriolytic properties. Moreover, Widal and Sicard * 

 found that the blood serum of frogs inoculated with typhoid bacilli 

 agglutinated these microorganisms but had no bacteriolytic action on 

 them, and, indeed, the typhoid bacilli may retain both life and viru- 

 lence after long residence in the lymph sacs of such frogs, 



Bordet' treated guinea-pigs at intervals with injections of the de- 

 fibrinated blood of rabbits and obtained from the former animals a 

 serum which in vitro dissolved the blood corpuscles of the latter 

 with great intensity, while the serum of normal guinea-pigs was 

 found to be without solvent action upon the corpuscles of the rabbit. 

 In these experiments it was observed that the serum first aggluti- 

 nated and then dissolved the erythrocytes ; but more extended 

 investigation showed that agglutination does not always precede so- 

 lution. Moreover, Bordet demonstrated that even in this case ag- 

 glutination and hemolysis are not identical or due to the same sub- 

 stances, inasmuch as he found that a temperature of 55° deprived 



' DetUsche med. Woehe/nschriji, 1896. 

 « Ceniralhlatt f. Bakterwlocfie, 20. 

 ^ Munchener med. Wockenschrift, 1894. 

 * Oompt. Bend. Soe. de Biol., 11, XI. 

 5 AmuUes de V JnstUut Pasteur, 12. 



