28O MANUAL OF BACTERIOLOGY. 



media, but grows best on Loffler's blood-serum mixture. 

 On this medium the growth consists of small white or cream- 

 colored, slightly elevated colonies, which may become con- 

 fluent. The morphology of the bacillus is most character- 



Bacillus of diphtheria stained by Xeisser's method. (X 1000.) 



istic when it is cultivated on blood-serum. It also grows 

 upon glycerine-agar. On potato it produces an invisible 

 growth (see Bacillus of Typhoid Fever). In alkaline 

 bouillon containing dextrose (or muscle-sugar) the reaction 

 becomes acid in forty-eight hours. The reaction of the 

 bouillon subsequently becomes alkaline. The growth may 

 form a pellicle over the surface of the bouillon. It has also 

 been successfully cultivated on various media to which egg- 

 albumen has been added. 



It is killed by a temperature of 58 C. in ten minutes. 

 It resists desiccation well. 



Bacteriological diagnosis of Diphtheria. In many large 

 cities the bacteriological diagnosis of diphtheria is under- 

 taken bv boards of health. The methods used differ some- 



