STAB AND SLANI CULTUBES. 303 



be seen, but they are so small as not to be detectable by 

 the unaided eye. 



In bouillon which is kept at a temperature of 35- 

 37 C. for a long time, a soft, whitish pellicle often 

 forms over a part of the surface. 



Changes in reactions of the bouillon. The reaction of 

 the bouillon frequently becomes at first acid, and, sub- 

 sequently, again alkaline, changes which can be observed 

 in cultivations in bouillon to which a little rosolic acid 

 has been added. This play of reactions has been 

 attributed to the primary fermentation of muscle sugar 

 that is often present in the bouillon. 



POTATO. On potato at a temperature of 35-37 C. 

 its growth after several days is entirely invisible ; only 

 a thin, dry glaze appearing at the point at which the 

 potato was inoculated. Microscopic examination of 

 scrapings from the potato, after twenty-four hours at 

 35-b7 C., reveals a decided increase in the number of 

 individual organisms planted. 



STAB AND SLANT CULTURES. In stab and slant 

 cultures on both gelatin and glycerin-agar-agar, the sur- 

 face growth is seen to predominate over that along the 

 track of the needle in the depths of the media. 



Isolated colonies on the surface of either of the media 

 in this method of cultivation present the same charac- 

 teristics that have been given for the colonies on plates. 



The growth in simple stab cultures does not extend 

 laterally very far beyond the point at which the needle 

 entered the medium. 



It is a non-motile organism. 



It does not form spores. 



It is killed in ten minutes by a temperature of 

 58 C. 



