6oo Micro-organisms of the Plague Group 



Pathogenesis. The introduction of cultures of this 

 bacillus into chickens, geese, pigeons, sparrows, mice, and 

 rabbits is sufficient to produce fatal septicemia. Feeding 

 chickens, pigeons, and rabbits with material infected with 

 the bacillus is also sufficient to produce the disease. Guinea- 

 pigs, cats, and dogs seem immune, though they may succumb 

 to large doses if given intraperitoneally. The organism is 

 probably harmless to man. 



Fowls ill with the disease fall into a condition of weakness 

 and apathy, which causes them to remain quiet, seemingly 

 almost paralyzed, and the feathers ruffled up. The eyes 

 are closed shortly after the illness begins, and the birds 

 gradually fall into a stupor, from which they do not awaken. 

 The disease is fatal in from twenty-four to forty -eight hours. 

 During its course there is profuse diarrhea, with very fre- 

 quent fluid, slimy, grayish-white discharges. 



Lesions. The autopsy shows that when the bacilli are 

 introduced subcutaneously a true septicemia results, with 

 the formation of a hemorrhagic exudate and gelatinous 

 infiltration at the seat of inoculation. The liver and spleen 

 are enlarged; circumscribed, hemorrhagic, and infiltrated 

 areas occur in the lungs; the intestines show an intense 

 inflammation with red and swollen mucosa, and occasional 

 ulcers following small hemorrhages. Pericarditis is fre- 

 quent. The bacilli are found in all the organs. If, on the 

 other hand, the disease has been produced by feeding, the 

 bacilli are chiefly to be found in the intestine. Pasteur 

 found that when pigeons were inoculated into the pectoral 

 muscles, if death did not come on rapidly, portions of the 

 muscle (sequestra) underwent degeneration and appeared 

 anemic, indurated, and of a yellowish color. 



Immunity. Pasteur* discovered that when cultures are 

 allowed to remain undisturbed for several months, their 

 virulence becomes greatly lessened, and new cultures trans- 

 planted from them are also attenuated. If chickens be 

 inoculated with such attenuated cultures, no other change 

 occurs than a local inflammatory reaction that soon disap- 

 pears and leaves the birds protected against future infec- 

 tion with virulent bacilli. From these observations Pasteur 



* An interesting account of Pasteur's experiments upon chicken-chol- 

 era can be found in the "Life of Pasteur, " by Vallery-Radot, translated 

 by Mrs. R. S. Devonshire, 1909. Popular Edition, New York, Double- 

 day, Page and Co. 



