406 BACTERIOLOGY. 



brown color, and finely granular. The superficial 

 colonies, however, particularly when young, are often 

 quite characteristic; they are transparent, bluish-white 

 in color, with an irregular outline, not unlike a grape- 

 leaf in shape. Slightly magnified they appear homo- 

 geneous in structure, but marked by a delicate network 

 of furrows. 



In stick cultures in gelatin the growth is mostly on the 

 surface, appearing as a thin, scalloped extension, which 

 gradually reaches out to the sides of the tube. In the 

 track of the needle there is but a limited growth, which 

 may be streaked, granular, or uniform in structure, and 

 of a yellowish-brown color. There is no liquefaction. 



Growth in Bouillon. This medium is uniformly 

 clouded by the typhoid bacillus, but the clouding is not 

 so intense as by the colon bacillus. A film is frequently 

 formed on the surface after eighteen to twenty-four 

 hours' growth. A very slight amount of acid is pro- 

 duced. 



Growth on Agar. The streak cultures on agar are 

 not distinctive; a transparent, grayish streak is formed. 



Growth on Potato. The growth on this medium 

 has been held by some to be very important, but it 

 varies considerably. When characteristic the growth 

 is invisible, but luxuriant, usually covering the surface 

 of the medium, and when scraped with the needle offers 

 a certain resistance. In some cases, however, the 

 growth is restricted to the immediate vicinity of the 

 point of inoculation, not very luxuriant, and of the 

 same color as the potato. Again, the growth may be 

 quite heavy and colojred yellowish-brown, and with a 

 greenish halo, when it is very similar to the growth of 

 the colon bacillus. These differences of growth on this 



