DESCRIPTIONS OF PATHOGENIC BACTERIA. 183 



the poison is consequently doubtful (cf. p. 123). 

 Endospores have not been observed, and C. 

 Frankel has noticed occasional branched fila- 

 ments. It is, then, evident that the position of 

 the diphtheria germ in our system of classifica- 

 tion is not clear ; in any case, the germ is not a 

 typical bacillus. Cultures develop between 18 

 42, best in blood serum to which bouillon 

 and sugar have been added, not so well upon 

 glycerin agar. The colonies are white and 

 usually remain distinct from one another ; up- 

 on serum is formed a delicate white incrusta- 

 tion ; in gelatin stab-cultures a scanty growth 

 develops in the form of small white colonies. 

 In broth, small grayish crumbs are formed 

 which sink to the bottom ; rarely a diffuse 

 clouding occurs; milk is coagulated by the 

 growth of the bacteria. Guinea-pigs are es- 

 pecially sensitive to inoculation ; somewhat 

 less so are rabbits, young dogs, sheep, goats, 

 horses, pigeons, and fowls. (The ordinary 

 spontaneous diphtheria of fowls and pigeons is 

 an altogether different disease). In the ani- 

 mals named above there arises, just as in man, 

 a necrotic inflammation of the mucous mem- 

 brane and, proceeding from this, an acute 

 poisoning often accompanied by paralysis. 

 The diphtheria bacteria have been found in 

 man in the diphtheritic incrustation of the 



