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 colored 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 
