828 PATHOGENIC MICROORGANISMS 



The bacillus is easily cultivated from the blood and organs of 

 infected animals, it grows well upon the simplest media at tempera- 

 tures varying from 25 to 40 C. In broth, it produces uniform 

 clouding with later a formation of a pellicle. Upon a gar it forms, 

 within twenty-four to forty-eight hours, minute colonies, white or 

 yellowish in color, which are at first transparent, later opaque. Upon 

 gelatin, it grows without liquefaction. Upon milk, the growth is 

 slow and does not produce coagulation. According to Kruse, 36 indol 

 is formed from pepton bouillon. Acid, but no gas, is formed in sugar 

 broth. 



Among barnyard fowl, this disease is widely prevalent, attacking 

 chickens, ducks, geese, and a large variety of smaller birds. The 

 infection is extremely acute, ending fatally within a few days. It 

 is accompanied by diarrhea, often with bloody stools, great exhaus- 

 tion, and, toward the end, a drowsiness bordering on coma. Autopsy 

 upon the animals reveals hemorrhagic inflammation of the intestinal 

 mucosa, enlargement of the liver and spleen, and often broncho- 

 pneumonia. 



The specific bacilli may be found in the blood, in the organs, 

 in exudates, if these are present, and in large numbers in the dejecta. 

 Infection takes place probably through the food and water con- 

 taminated by the discharges of diseased birds. 37 



Subcutaneous inoculation or feeding of such animals with pure 

 cultures, even in minute doses, gives rise to a quickly developing 

 septicemia which is uniformly fatal. The bacillus is extremely 

 pathogenic for rabbits, less so for hogs, sheep, and horses, if infection 

 is practiced by subcutaneous inoculation. Infection by ingestion 

 does not seem to cause disease in these animals. 



Historically, the bacillus of chicken cholera is extremely in- 

 teresting, since it was with this microorganism that Pasteur 35 carried 

 out some of his fundamental researches upon immunity, and suc- 

 ceeded in immunizing chickens with attenuated cultures. The first 

 attenuation experiment made by Pasteur consisted in allowing the 

 bacilli to remain in a broth culture for a prolonged period without 

 transplantation. With minute doses of such a culture (vaccin I) 

 he inoculated chickens, following this, after ten days, with a small 

 dose of a fully virulent culture. Although enormously important 

 in principle, the practical results from this method, as applied to 



88 Kruse, in Fliigge 's ' ' Die Mikroorganismen. ' ' 



87 Salmon, Rep. of the Com. of Agriculture, 1880, 1881, and 1882. 



