286 BAGTERIOLOQY. 



still be seen, but they are so small as not to be detect- 

 able 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 becomes at first acid, and, subsequently, 

 again alkaline, changes which can be observed in 

 cultivations in bouillon to which a little rosolic acid 

 has been added. 



Potato. — On potato at a temperature of 35°-37° C. 

 its growth after several days in entirely invisible ; only 

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

 potato was inoculated. Microscopic examination of 

 the potato after twenty-four hours at 35°-37° C. shows 

 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 

 surface 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 ol 

 58° C. 



It grows at temperatures ranging from 22° C to 



