216 Chapter VIII 



clumps, it might be asked whether this agglutinative substance might 

 not be the substance, stable under heat, which is necessary for the 

 production of Pfeiffer's phenomenon. For some time, indeed, it was 

 believed that this phenomenon is due to the microcytase acting on 

 vibrios which have first been modified by the agglutinative sub- 

 stance. This latter substance resists heating to 55 56 C., is only 

 destroyed at higher temperatures, and is retained in the blood serum 

 long after the cytase has entirely disappeared. The analogy between 

 the agglutinative substance of the fluids of animals that have acquired 

 immunity and the substance in the same fluids that is stable under 

 heat is undeniable, and yet these two substances are not identical. 

 A whole series of observations, which we shall presently describe, 

 demonstrate this thesis clearly. A serum may be highly agglutinative 

 without being capable of bringing about the transformation of vibrios 

 into granules ; the converse also holds good. The substance which sets 

 up Pfeiffer's phenomenon, and which is found in the fluids of immunised 

 guinea-pigs, is a "fixative substance" analogous to those we have 

 already met with in the serums of animals so adapted that they are 

 able to resorb the various cell elements. As in the resorption of cells, 

 so also in the destruction of micro-organisms, the fixatives are specific. 

 The substance which aids the transformation into granules is not only 

 distinct from the fixatives which sensibilise red blood corpuscles or 

 spermatozoa, but also from the fixatives which sensibilise bacteria. 

 This specificity has been demonstrated and carefully studied by 

 Pfeiffer, who has shown that it may even serve to distinguish species 

 [228] of bacteria. The serum of a guinea-pig which has been immunised 

 against the cholera vibrio, will render sensitive these vibrios, and 

 these only, to the action of the microcytase. Even allied vibrios, 

 such as various water vibrios, for example, are not sensitive to the 

 fixative of anticholera serum. On the other hand, the serums ob- 

 tained after the inoculation of these aquatic vibrios are incapable of 

 producing granular transformation in the cholera vibrio. 



When we inject into one and the same animal several species 

 of vibrios we obtain a serum or a peritoneal fluid which produces 

 Pfeiffer's phenomenon with the vibrios of all the species which have 

 been used to make the inoculations. This anti vibrio serum contains 

 only a single cytase for the vibrios, but contains as many different 

 fixatives as there were species inoculated. 



The transformation of vibrios into granules, when produced in a 

 high degree against virulent vibrios, under the influence of the body 



