466 MICRO-ORGANISMS AND DISEASE [chap. 



But Pfeififer i has shown that while the vibrio Metchnikovi 

 is virulent for the pigeon the vibrio of cholera is not, and 

 further that a pigeon that had received first a large dose of 

 cholera vibrios succumbs to a further injection of the vibrio 

 Metchnikovi just like any normal pigeon. That pigeons are 

 insusceptible to subcutaneous and intermuscular injection 

 can be easily shown ; I have injected into the pectoral 

 muscle as much as 2-3 cc. of recent active broth culture, and 

 on searching by the culture test and film specimens twenty- 

 four hours afterwards for comma bacilli no trace of them 

 could be discovered. The pigeons were and remained 

 perfectly normal. 



Vibrio Metchnikovi differs then from the vibrio of cholera 

 as regards the guinea-pig, the former being very virulent 

 injected subcutaneously. Metchnikoff has shown that 

 guinea-pigs can be immunised by successive inoculations 

 of non-fatal doses of culture, and that the blood-serum of 

 such animals also possesses germicidal action and can confer 

 passive immunity to guinea-pigs against an otherwise fatal 

 dose of the vibrio ; and further that the germicidal action of 

 the serum of an immunised animal exhibits this germicidal 

 action against the vibrio Metchnikovi already in vitro. 



{n.) Spirillum Obenneyeri of relapsing fever. — Obermeyer 

 {Centralbl. f. d. med. TFiss., 1873, No. 10) discovered in the 

 circulating blood of patients affected with this fever, during 

 the febrile stage, innumerable spirilla actively motile : they 

 disappear from the blood immediately preceding the end of 

 the febrile stage. 



The spirilla are very thin and about 20-30-40 yu,. long ; 

 their movement is that of rapidly progressing spirals. Koch 

 has demonstrated by photography of dried and stained speci- 

 mens the jjresence of the flagella in the spirilla. '\\''eigert 



' Zeilschrift f. Hygiene, vii. 3. 



