6o6 Micro-organisms of the Plague Group 



gelatinous infiltration at the seat of inoculation. The liver and spleen are en- 

 larged; circumscribed, hemorrhagic, and infiltrated areas occur in the lungs; the 

 intestines show an intense inflammation with red and swollen mucosa, and occa- 

 sional ulcers following small hemorrhages. Pericarditis is frequent. 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 the bacilli were inoculated into the pectoral muscles of pigeons, it 

 death did not come on rapidly, portions of the muscle (sequestra) underwent 

 degeneration and appeared anemic, indurated, and of a yellowish color. 



TmnittTiity. — Pasteur* discovered that when cultures are allowed to remain un- 

 disturbed for several months, their virulence becomes greatly lessened, and new 

 cultures transplanted from them are also attenuated. If chickens be inoculated 



Fig. 241. — Bacillus of chicken-cholera, from the heart's blood of a pigeon. 

 X 1000 (Frankel and Pfeiffer). 



with such attenuated cultures, no other change occurs than a local inflammatory 

 reaction that soon disappears and leaves the birds protected against future 

 infection with virulent bacilli. From these observations Pasteur worked! out 

 a system of protective vaccination in which the fowls are first inoculated 

 with attenuated, then with more active, and finally with virulent, cultures, 

 with resulting protection and immunity. 



Use has been made of this bacillus to kill rabbits in Australia, where they are 

 pests. It is estimated that two gallons of bouillon culture vnJl destroy 20,000 

 rabbits, irrespective of infection by contagion. 



The bacillus of chicken-cholera may be identical with organisms found in 

 various epidemic diseases of larger animals, and, indeed, no little confusion has 

 arisen froin the description of what is now pretty generally accepted to be the 

 same organism as the bacillus of rabbit septicemia (Koch), Bacillus cuniculicida 

 (Flugge), baciUus of "Wildseuche" (Huppe), baciUus of "^Biiffelseuche" (Oriste- 

 Armanni), etc. 



* An interesting account of Pasteur's experiments upon chicken-cholera can be 

 found in. the "Life of Pasteur," by Vallery-Radot, translated by Mrs. R. S. 

 Devonshire, 1909. Popular Edition, New York, boi[bledsiy,]E;^ge and Co. 



