316 



BACILLI PATHOGENIC IN ANIMALS. 



under a low power to be discs of a yellowish-brown 

 colour with sharp outlines, finely granular, seldom 

 circular, but as a rule with irregular boundaries. 

 The centre is of a lightish-yellow colour, towards the 

 periphery there is a narrow brownish ring, and then a 

 light border. The superficial colonies form small moder- 

 ately prominent, transparent drops of a yellowish-white 



m il^m/' : : 



Fig. 90. Chicken cholera. 

 Section from the liver of a hen X 700. 



colour, they show less of a circular form and are dis- 

 tinctly granular ; but the zones above mentioned can 

 still be recognised, and have only become correspond- 

 ingly broader. In puncture cultivations they form 

 partly discrete and partly confluent colonies along the 

 needle track ; on the surface they spread out in a flat 

 layer, which is somewhat more marked than in the case 

 of the bacilli of rabbit septicaemia. On blood serum the 

 cultivations form a dull, white, thin layer. On potatoes 

 a wax- like transparent greyish-white and only slightly 

 prominent layer is formed, which grows slowly and only 

 at a temperature of about 28 C. Growth of the bacilli 

 also occurs on hard-boiled white of egg. In neutralised 

 broth they grow luxuriantly, and cause slight turbidity 

 of the fluid. According to Pasteur they soon lose their 

 vitality in neutralised urine ; they do not grow at all in 

 yeast water. 



