Facts bearing on acquired immunity 225 



a short time are completely digested. This fact, of such constant 

 occurrence in the phagocytosis of the vibrios, furnishes us with still 

 another proof of the microphagic origin of microcytase. 



If Pfeiffer's phenomenon is merely a particular instance of the trans- 

 formation of vibrios into granules in fluids containing microcytase, 

 it is quite natural that its suppression should not involve a fatal 

 infection of the vaccinated animals. On the other hand, if the phago- 

 cytic reaction, so widely different, really plays an important part 

 in acquired immunity, everything that interferes with phagocytosis 

 must at the same time compromise the refractory condition. With [237] 

 the object of solving this question Cantacuzene 1 , working in my 

 laboratory, undertook a detailed investigation of this point. He 

 showed that the injection of opium, in a non-fatal dose, narcotised 

 the guinea-pig and at the same time prevented the movements of 

 the leucocytes. Small glass tubes containing cholera vibrios and 

 introduced beneath the skin of vaccinated guinea-pigs, became filled 

 with numbers of leucocytes in the non-narcotised animal; in the 

 guinea-pig that had received tincture of opium, the tubes left for 

 several hours contained no leucocytes and later only did they begin 

 to enter the tubes. When a strong dose of cholera vibrios was 

 injected into the peritoneal cavity of thoroughly vaccinated guinea- 

 pigs, the animals easily resisted the inoculation. When, however, 

 similarly vaccinated guinea-pigs were submitted to the influence of 

 tincture of opium, the same dose of vibrios caused their death. In 

 these narcotised animals, in spite of the considerable dilatation and 

 hyperaemia of the vessels and in spite of the marked hyperleucocytosis 

 of the blood, diapedesis was not produced during the first few hours 

 after the injection of theopium, and it was not till later (5 to 6 hours 

 after injection) that the leucocytes began to appear in the peritoneal 

 cavity. The vibrios profit by the period of inactivity of the phago- 

 cytes to multiply, retaining their motility and also the property of 

 staining with basic aniline dyes. When the retarded leucocytes make 

 their appearance in the peritoneal cavity, they find it already invaded 

 by a multitude of vibrios. In spite of this the leucocytes, especially 

 the microphages, ingest an enormous number of the organisms ; this 

 does not prevent the death of the guinea-pigs, though it takes place 

 some hours later than in the unvaccinated control animals. At the 

 moment of death, free vibrios are no longer found in the exu- 

 dation ; they have all been ingested by the microphages, inside 



1 Ann. de FInst. Pasteur, Paris, 1898, t. xii, p. 288. 



15 



