432 BACTERIOLOGY. 
gelatin after the agar is thoroughly melted, so as not 
to alter this ingredient by prolonged exposure to high 
temperature. The glucose is added after clearing. 
The medium must contain 1.5 per cent. of normal 
acid. , 
Growth of the Colonies. 'The growth of the typhoid. 
bacilli in plates made from the medium as above de- 
scribed gives rise to small colonies with irregular out- 
growth and fringing threads (Figs. 54 and 55). The 
fe te 
Colony of typboid bacilli more highly magnified. (Hiss.) 
colon colonies, on the other hand, are much larger, 
and, as a rule, are darker in color and do not form 
threads. The growth of the typhoid bacilli in tubes 
produces uniform clouding at 37° C. within eighteen 
hours. The colon cultures do not give the uniform 
clouding, and present several appearances, probably 
dependent upon differences in the degree of their 
motility and gas-producing properties in media. Some 
of the varieties of the colon bacillus grow only locally 
