326 PATHOGENIC BACTERIA. 



The cultures upon gelatin plates after about two days 

 appear as small white points. The deep colonies reach 

 the surface slowly, and do not attain any considerable 

 size. The gelatin is not liquefied. The microscope 



FIG. 105. Bacillus of chicken-cholera, from the heart's blood of a pigeon ; 

 x 1000 (Frankel and Pfeiffer). 



shows the colonies to be irregularly rounded disks with 

 distinct smooth borders. The color is yellowish-brown, 

 and the contents are granular. Sometimes there is a dis- 

 tinct concentric arrangement. 



In gelatin puncture-cultures a delicate white line occurs 

 along the entire path of the wire. When viewed through 

 a lens, this line can be seen to consist of aggregated mi- 

 nute colonies. If, instead of a puncture, the inocula- 

 tion be made upon the surface of obliquely solidified 

 gelatin, a much more pronounced growth takes place, 

 and along the line of inoculation a dry, granular coat- 

 ing is formed. This growth is quite similar to that 

 upon agar-agar and blood-serum, which growths are 



