520 PATHOGENIC BACTERIA. 



readily at ordinary temperatures, but best at 37 ° C. By 

 employing suitable methods it can be found in the organs 

 of yellow fever cadavers, usually united in little groups, 

 always situated in the small capillaries of the liver, kid- 

 ney, etc. The best method of demonstration is to keep 

 a fragment of liver, obtained from a body soon after 

 death, in the incubator at t>7° C. for twelve hours and 

 allow the bacteria to multiply in the fresh tissue before 

 examination. 



The bacillus can be cultivated upon the ordinary 

 media. Upon gelatin plates it forms rounded, transpar- 

 ent, granular colonies, which during the first three or 

 four days present somewhat the appearance of leukocytes. 

 The granular appearance becomes continuously more 

 marked, and usually a central or peripheric nucleus, 

 completely opaque, is seen. In time the entire colony 

 becomes opaque, but does not liquefy gelatin. 



Stroke-cultures on obliquely solidified gelatin exhibit 

 brilliant, opaque, little drops similar to drops of milk. 



In bouillon it develops slowly, without either pellicle 

 or flocculi. 



The culture upon agar-agar is said to be characteristic. 



If grown at 37 C, the peculiar appearances of the 

 colonies do not develop; but if the culture is kept at 20 - 

 22° C, the colonies appear rounded, whitish, opaque, and 

 prominent, like drops of milk. This appearance of the 

 colonies shows well if the cultures are kept for the first 

 twelve to sixteen hours at 37 C, and afterward at room- 

 temperature, when the colonies will show a flat central 

 nucleus, transparent and bluish, surrounded by a promi- 

 nent and opaque zone, the whole resembling a drop of 

 sealing-wax. Sanarelli refers to this appearance as con- 

 stituting the diagnostic feature of Bacillus icteroides. It 

 can be obtained in twenty-four hours. 



Upon blood serum the growth is very meagre. The 

 growth upon potato corresponds to the classic description 

 of that of the bacillus of typhoid fever. 



The bacillus is a facultative anaerobe. It slowly fer- 



