296 Diseases of Poultry 



The thermal death point (moist) is 56 to 57° C. for an 

 exposure of fifteen minutes. The optimum temperature is 

 35 to 37° C. 



Cultural Characters. Agar plates. — Small white colonies 

 make their appearance within twenty-four hours. They 

 increase in size slowly and seldom attain more than one 

 millimeter in diameter, even after three or four days' in- 

 cubation. Under the microscope they appear yellow and 

 vary in form, being oval, spindle-shaped or round. The 

 surface is usually marked with one or two rosette figures. 



Slant Agar. — The ordinary streak growth is quite visible 

 in twenty-four hours, and resembles that of the typhoid 

 bacillus. It spreads little and remains delicate even after 

 prolonged incubation. When, however, the entire surface 

 of the agar is streaked, with a platinum loop, the charac- 

 teristic cultural appearance of the common pus streptococcus 

 is obtained. The growth is not continuous and compact, 

 but consists of minute, delicate colonies, which may be so 

 small as to require a magnifying lens for detection. This 

 cultural characteristic is of extreme importance in identifi- 

 cation work. 



Gelatin Plates. — Small white colonies may be seen in 

 forty-eight hours. They remain small for several days, 

 and only under exceptional conditions do they develop into 

 characteristic surface colonies which to a certain extent 

 resemble the grape-leaf colony of B. typhosus. 



Gelatin Stab. — A delicate growth occurs in forty-eight 

 hours along the whole line of inoculation. In litmus milk 

 little or no apparent change occurs within the first forty- 

 eight hours, after which the milk becomes slightly acidified 

 without any signs of coagulation of the casein. 



Gas Production in Sugar Bouillon. — Negative results were 

 obtained with maltose, lactose, saccharose, inulin, and 

 dextrin bouillon. Dextrose and mannite were attacked, 



