226 Chapter VIII 



which they have undergone granular transformation. On making a 

 post-mortem examination of the animal a large number of small 

 heaps of vibrios, such as are never met with in animals that have 

 not been submitted to the action of opium, are found on the omentum. 



All that is necessary, then, is to retard the phagocytic reaction 

 for a few hours in order to cause well-vaccinated guinea-pigs to 

 succumb to the action of the vibrios. One can readily understand 

 that, with this result before us, there can be no hesitation in at- 

 tributing to phagocytosis a much more important part in assuring 

 acquired immunity than to Pfeiffer's phenomenon. 



The study of other diseases produced by vibrios only serves to 

 corroborate the general conclusions that follow from the detailed 

 study of the essential processes in acquired immunity against the 

 cholera vibrio. It is here necessary to recall the discovery by 

 v. Behring and Nissen of the very marked bactericidal power of 

 the blood serum of guinea-pigs that have been vaccinated against 

 Gamaleia's vibrio. When this fact was first demonstrated we were 

 justified in thinking that the vibrionicidal property of the blood 

 might by itself explain this acquired immunity ; but a comparative 

 study of the phenomena which take place in vitro with those which 

 take place in the living animal, soon demonstrated how slight was 

 the foundation for this hypothesis. Whilst the vibrios, when sown 

 in the blood serum of hypervaccinated guinea-pigs, there perished 

 in large quantities or even the whole of them, these same organisms, 

 when inoculated into the subcutaneous tissue of the same animals, re- 

 mained alive for several days. Gamaleia's vibrio is much less capable 

 of being transformed into granules than is the cholera vibrio, and we 

 find it retaining its normal form even inside the leucocytes. There is 

 no occasion in this case, therefore, to look for Pfeiffer's phenomenon. 



The rapid and marked destruction of Gamaleia's vibrio, in vitro, 

 in the blood serum of vaccinated guinea-pigs, and the prolonged 

 survival of these organisms in the living animal, afford additional 

 evidence that the two groups of phenomena cannot be identical. 

 On the other hand, it furnishes a further proof that, during the 

 preparation of the serum, there is produced, parallel with the co- 

 agulation, another process which confers bactericidal power on the 

 serum. It is quite evident that, as in the case of the cholera vibrio, 

 we have here to do with the liberation of microcytase at the 

 expense of the destroyed or injured leucocytes. Acting along with 

 the specific fixative of the body fluids, this cytase causes the death 



