436 BACTERIOLOGY. 
nies sometimes present much the same appearance, 
However, it was found that the typhoid colonies usu- 
ally grew near the surface, while the colon colonies, 
which are small and white, are almost invariably very 
deep. This is especially true after forty-eight hours; 
therefore, if one is not sure of a colony from the 
appearance, an attempt to “‘fish’’ it will usually 
identify it. 
To one familiar with the medium, the characteristic 
appearance of a plate when typhoid is present is almost> 
unmistakable, and it would seem that one would be 
almost sure to find the typhoid in some one of a 
series of plates, even if there were but few in the 
specimen. 
Elsner says that the typhoids do not develop for 
forty-eight hours. Although the differentiation is 
more accurate after that time, still for practical 
methods of work twenty-four hours was found to be 
quite sufficient. When the plates are first taken from 
the incubator the diagnosis is not quite as certain, for 
the colon colonies will not have developed the charac- 
teristic color; but if the plates be allowed to stand in 
the light for a couple of hours the diagnosis will be 
found quite easy. After forty-eight hours all the large 
colonies will be colon and most of the small ones 
typhoid, if there be any typhoid present. Even after 
several days’ standing in the ice-chest the typhoid colo- 
nies do not develop color. 
Except for the difficulty in obtaining an exact tem- 
perature for growth and a cool room for examination, 
this method was found very satisfactory. 
Tae CapaLpr Pirate Meprum. In his original 
paper, Capaldi gives the following recipe: 
