BACTERIUM DIPHTHERIA 463 



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 characteristics 

 that have been given for the colonies on plates. 



The growth in simple stab-cultures does not extend later- 

 ally 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 bacillus in 

 sections of diphtheritic membrane, both the Gram method 

 and the fibrin method of Weigert give excellent results. 



Pathogenic Properties. — When inoculated subcutaneously 

 into the bodies of susceptible animals the result is not the 

 production of septicemia, as is seen to follow the introduc- 

 tion into animals of certain other organisms with which 



