TEXT-BOOK OF BACTERIOLOGY. 337 



lowish-brown color, particularly distinguished by a concentric 

 stratification and a slightly-granular texture. 



In the test-tube there is gradually developed, along the entire 

 inoculation puncture, a white and delicate streak which proves later 

 on to be composed of single small granules. They grow slightly 

 on the surface. But surface cultures on oblique gelatin extend 

 rather widely; in the neighborhood of the point of inoculation a 

 dry, grayish-white, elevated coating arises, which adheres firmly 

 and tenaciously to the medium. 



On oblique agar, and on solidified blood-serum, a whitish, shin- 

 ing, moderately thick coating is formed. 



The bacteria do not thrive on potatoes at ordinary temperature; 

 a scanty, yellowish-brown, transparent growth is developed in a 

 few days. 



Successful transmissions from such cultures to susceptible ani- 

 mals may be made in various ways. By inoculation or subcutane- 

 ous application, not only fowls and geese, but also pigeons and 

 sparrows, mice and rabbits can be infected; but Guinea-pigs are 

 rather, insusceptible and only succumb to large quantities of the 

 poisonous substance introduced directly into the abdominal cavity 

 or blood-vessels. Mixed with the food of chickens, pigeons, mice, 

 and rabbits, the disease may be produced in the most pronounced 

 manner, and the symptoms referable to the alimentary canal (pro- 

 minent under natural conditions) will appear with great distinctness. 



Post mortem the bacteria (no matter how they were introduced) 

 are found in the blood and all organs, and the affection due to the 

 subcutaneous application is plainly characterized as genuine septi- 

 caemia. The subcutaneous cellular tissue in the neighborhood of the 

 point of inoculation is, besides, usually in a state of hemorrhagic in- 

 flammation and infiltration ; if transmission has been effected by feed- 

 ing, the intestinal mucous membrane is the chief seat of the changes. 



One of the new procedures should be applied to demonstrate 

 the rods within the tissue, since the bacilli of chicken cholera be- 

 long to the micro-organisms which readily fade under decoloration. 

 In good preparations large quantities of bacilli will then be seen 

 lying in the smaller blood-vessels, especially the capillaries. The 

 rods never invade the cells. 



Pasteur, as will be remembered, made his first observations 

 regarding the process of attenuation on the bacilli of chicken 

 cholera. He perceived that cultures exposed for some length of 

 time (for months) to the influence of the oxygen of the air (i.e., 

 preserved with simple wadding without any other means) lost their 

 virulence more or less and were no longer injurious to animals. 

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