STUDIES ON FOWL CHOLERA 281 



Amison, 1911, Hadley, 1912, 1914a, 1914b) has devoted some 

 attention to the problems of infection and resistance in the 

 organisms of the hemorrhagic septicemia group. Use has been 

 made of a highly virulent culture (strain 48) of B. avisepticus. 

 The lethal dose of this culture for rabbits has frequently stood at 

 0.000,000,000,001 cc. of a forty-eight-hour broth culture. Gal- 

 lagher (1917) in recent experiments, in which he employed the 

 same culture as the infective agent to test the immunizing power 

 of the writer's Culture 52, as well as of certain strains of cattle, 

 sheep and swine septicemia, used the strain in amounts of 

 0.000,000,001 cc, with regularly successful infections. Such a 

 strain should be well adapted for testing out the question of toxin- 

 production by B. avisepticus. 



EXPERIMENTAL 



In studies involving the attempt to immunize rabbits and 

 pigeons with killed cultures of strain 48, not yet reported, the 

 writer has had occasion to administer large doses of killed broth 

 culture. The following is a protocol: 



Eight rabbits (923-931) each received subcutaneously on October 

 17, 1912, 1 cc. of a forty-eight hour broth culture of strain 48 killed by 

 heating at 63°C. for thirty minutes; no illness resulted. Dose repeated 

 on November 21 and again on December 5; no result. 



On December 20, 1912, all the animals, together with two controls, 

 were infected by inoculation with 0.01 cc. of forty-eight hour broth 

 culture of strain 48. The controls and all but two of the principals died 

 in fourteen to forty hours. 



From the above test it may be concluded that the cultures 

 killed at a temperature usually regarded as too low to destroy 

 in toto extracellular toxins, if present, showed no toxicity for 

 rabbits in the amounts used; furthermore that they failed in all 

 but two instances to afford protection against infection with 

 living culture. 



Tests were also performed on pigeons, which are highly sus- 

 ceptible to intramuscular inoculation with the fowl cholera virus. 



Six pigeons were inoculated subcutaneously, at intervals of 



