282 TEXT-BOOK OF BACTERIOLOGY. 



The vibrio Metschnikoff is stained red by the addition of muri- 

 atic or, better still, sulphuric acid free from nitrite or peptonated 

 agents, just as the cholera vibrio, perhaps even more decidedly. 



There will now be no doubt that the cholera and Metschnikoff 

 vibrios are micro-organisms very nearly related to one another, 

 which can, perhaps, trace their pedigree to the same ancestors, but 

 have developed in the course of time in quite different directions. 

 While the one accustomed itself to man and obtained pathog-enic 

 properties for him, but can be transmitted to animals only artifi- 

 cially, if not forcibly, the other has subjected these very animals to 

 its pernicious influence. 



Gamaleia's and Pfeiffer's experiments have shown that the vibrio 

 Metschnikoff is pre-eminently infectious for chickens, Guinea-pigs, 

 and especially pigeons, while mice, for instance, are almost entirely 

 refractory. Transmission is better accomplished by the subcutane- 

 ous tissue, and this always results in success in the case of pigeons. 

 We may infect Guinea-pigs through the intestinal canal by means 

 of the method indicated by Koch for the cholera bacteria. 



The symptoms of disease are but little pronounced in every case, 

 In Guinea-pigs, however, we regularly notice in conjunction with 

 inoculation that after a rise of the body's temperature for a short 

 time, a very considerable fall of it down to 33 C. or even below 

 occurs. Death ensues in from twenty to twenty- four hours after 

 inoculation. 



Upon dissection (after the subcutaneous application) a bloody 

 oedema is found extending 1 over a wide area about the place of in- 

 fection, as well as a superficial necrosis of the tissue and vast quan- 

 tities of bacteria in the blood and all organs, and the entire affec- 

 tion confines itself so entirely to the vascular system that Pfeiffer 

 calls it vibrio septicaemia. Only slight changes and very few or no 

 micro-organisms are seen in the intestine; but if they had first 

 been introduced into the stomach, the digestive canal would be the 

 chief seat of the pathological processes, including an intense inflam- 

 mation and the presence of large numbers of vibrios. 



Though the vibrio Metschnikoff is exceedingly infective to pigeons 

 and Guinea-pigs, it is easy to grant immunity to these animals, as 

 Gamaleia has proved. This may best be obtained by means pf 

 sterilized cultures of the virulent bacteria. We have here an es- 

 pecially distinct proof of the fact (duly discussed above) that the 

 immunity obtained is mainly owing to the excretions of the inocu- 

 lated micro-organisms. It is a striking circumstance peculiar to 

 this case, that the substance supplying" protection is not even de- 

 stroyed by continued heating to 100 C. i.e., the nourishing fluids 



