340 



MANUAL OF BACTERIOLOGY. 



medium the growth consists of small white or cream-colored, 

 slightly elevated colonies, which may become confluent. The 

 morphology of the bacillus is most characteristic when it is culti- 

 vated on blood-serum. It also grows upon glycerin- agar, 

 On potato it grows only if the potato is first treated with soda 

 solution (i per cent.) so as to neutralize the acidity of this 

 medium.* In alkaline bouillon containing dextrose or muscle- 



P 



r 



^' "■) . - 



-? 





•Vi.-' 



.. *•* 



Fig. 87. — BaciHus of diphtheria stained by 

 Neisser's method. (X 1000.) 



Fig. 88. — Swab and culture- 

 tube used in the diagnosis of 

 diphtheria. 



sugar the reaction becomes acid in forty-eight hours, f The 

 reaction of the bouillon subsequently becomes alkaline. The 

 growth may form a pellicle over the surface of the bouilTon. It 

 has also been successfully cultivated on various media to which 

 egg-albumen has been added. 



It is killed by a moist heat at about 60° C. in ten minutes. 

 It is very resistant to drying. 



* Giinther. Loc. cit. 



fKoUe and Wassermann. Loc. cit. p. 769-770. 



