408 BACTERIOLOGY. 



from the potato, after twenty-four hours at 35-37 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. 



It grows at temperatures ranging from 22 to 37 

 C., but most luxuriantly at the latter temperature. 



Its growth in the presence of oxygen is more active 

 than when this gas is excluded. 



STAINING. In cover-slip preparations made either 

 from the fauces of a diphtheritic patient or from a pure 

 culture of the organism it is seen to stain readily with 

 the ordinary aniline dyes. It stains also by the method 

 of Gram, but the best results are obtained by the use 

 of Loffler's alkaline methylene-blue solution ; this brings 

 out the dark points in the protoplasmic body of the 

 bacilli and thus aids in their identification. 



For the purpose of demonstrating the Loffler bacil- 

 lus in sections of diphtheritic membrane, both the Gram 

 method and the fibrin method of Weigert give excellent 

 results. 



PATHOGENIC PROPERTIES. When inoculated sub- 



