Immunity against micro-organisms 303 



pigs, inoculated with the typhoid cocco-bacillus and simultaneously 

 subjected to the action of protective serums, the micro-organisms 

 lose their mobility almost immediately. A little later, they exhibit a 

 degeneration of form, become less refractile and disintegrate. After 

 the injection of large doses of specific serum the bacilli, much as in 

 the case of the cholera vibrio, become transformed into granules. 

 " But," say these authors, " this last mode of destruction, that is to 

 say the formation of granules at the expense of the injected bacteria, 

 does not occur with such remarkable regularity as it does in Pfeiffer's 

 phenomenon in the cholera vibrio" (p. 219). Whilst these changes 

 are going on in the peritoneal fluid, the leucocytes begin to come up 

 and to ingest the bacilli and their dtbris. "Phagocytosis, therefore, 

 undoubtedly plays a part in the destruction of the bacteria. Never- 

 theless, as most of the injected bacteria die in the fluid of the 

 exudation, phagocytosis can not be regarded as the cause of the 

 protective action of the serum " (p. 220). We see from this descrip- 

 tion that even in the case of the typhoid cocco-bacillus the direct 

 action of the fluids of the body is perceptibly less marked than in 

 the case of the cholera vibrio. Even in the latter, however, it is 

 necessary to make many reservations. The same laws apply to the 

 immunity against this micro-organism, conferred by the serum of 

 immunised animals, as to the immunity due to vaccinations by the 

 vibrios or their products. To treat this subject fully one would have 

 to repeat almost textually the two preceding chapters, but I will 

 simply recall the fact that this transformation, almost general and 

 very rapid, as we observed in vitro in vibrios placed in contact with 

 fresh specific serum or with the mixture of this serum, heated to 

 65 56 C., and normal unheated serum, is only met with in the 

 animal body where phagolysis appears. Pfeiffer first observed 

 the phenomenon which bears his name in the peritoneal cavity, 

 and it is best seen in that situation during the period of the 

 phagolysis of the white corpuscles. Vibrios, mixed with small doses [319] 

 of specific serum which by itself is able to render them motionless 

 and agglutinate them, but which is absolutely unable to transform 

 them into granules, present this transformation immediately they are 

 introduced into the peritoneal cavity of normal guinea-pigs. In this 

 case the vibrios, permeated by the fixative of the specific serum, are 

 affected by the microcytase which has escaped from the injured 

 phagocytes and is found in the peritoneal fluid. The preparation of 

 the peritoneal cavity of normal guinea-pigs by means of an injection 



