318 Chapter X 



by itself, is also incapable of averting a fatal issue, Wassermann 

 obtains an absolute immunity of his animals. This immunity is due, 

 according to Wassermann, to the cytase of the ox serum acting along 

 with the fixative of the specific serum. The united action of the two 

 ferments causes the death of the micro-organisms. Besredka 1 has 

 justly observed that normal ox serum contains, in addition to cytases, 

 a substance which exerts a distinct agglutinative action on the typhoid 

 cocco-bacillus and another which stimulates the phagocytic action. 

 These two substances resist a temperature of 55 60 C., and Besredka 

 [334] shows that with normal ox serum, deprived of its cytases by heating 

 as above, we can obtain the same protective effect as with the same 

 serum unheated. 



As the result of another series of experiments, Wassermann 2 

 recognises the immunising action of normal serum heated to 60 C. 

 and so entirely deprived of its cytases. Into the peritoneal cavity of 

 guinea-pigs he injects, mixed with heated normal rabbit's serum, a 

 dose of typhoid cocco-bacilli several times greater than the lethal dose. 

 The guinea-pigs resist this completely. Analysing the mechanism of 

 this immunity, Besredka (Ic. p. 229) attributes it to the combined 

 action of the agglutinin and of the substance which stimulates the 

 phagocytes. We have here another proof that the stimulins which 

 play such an important part in immunity conferred by serums, are 

 found not only in the specific serums, but also in normal serums, 

 whether unheated or heated to 55 60 C. 



The protective property of the normal serums of man and animals 

 against the cholera vibrio has already been referred to. We may now 

 go a little more deeply into the mechanism by which these serums 

 act This task is an easy one thanks to the important work by Issaeff 3 

 carried out in R Pfeiffer's laboratory. Having confirmed the ob- 

 servation, made by other investigators, that blood serum from the 

 human subject, whether in health or affected by any disease, is capable 

 of protecting the guinea-pig against the cholera vibrio provided that 

 it is injected 24 hours before the micro-organisms, Issaeff studied the 

 phenomena observed in the peritoneal cavity of the animals experi- 

 mented upon. By means of small capillary pipettes he drew off at 

 intervals a small quantity of fluid from the peritoneal cavity and 

 examined it in hanging drop or in stained preparations. Some time 



1 Ann. de I'lnst. Pasteur, Paris, 1901, t. xv, p. 225. 



2 Deutsche med. Wchnschr., 1901, S. 4. 



3 Ztschr.f. Hyg., Leipzig, 1894, Bd. xvr, S. 287. 



