STAINING. 333 



has been added. This play of reactions has been attrib- 

 uted 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, there 

 being only a thin, dry glaze appearing at the point at 

 which the potato was inoculated. Microscopic examin- 

 ation of scrapings 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 

 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 of 58° C. 



It grows at temperatures ranging from 22° C. 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 those obtained by the 

 use of Lneffler's alkaline methylene-blue solution; this 



15* 



