DIPHTHERIA BACILLUS 127 



Small granules, the Babes-Ernst granules, are shown by 

 the special staining of Neisser. 



Properties. B. diphtheria is immobile; does not liquefy 

 gelatin. Is not very resistant, being destroyed by a tempera- 

 ture of 50 C., but may live on blood-serum for months. 

 Acid is produced in sugar media. 



Growth. Grow readily on all media, but best on blood- 

 serum mixtures, between temperatures of 20 and 40 C. 

 They are facultative anaerobic; they grow quite rapidly and 







* * 



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* . : 



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Fig. 53- Diphtheria bacilli from a culture on blood-serum, stained 

 by Loffler's methylene-blue solution, showing deeply stained points 

 (X2ooo) (Wright and Brown). 



profusely. Egg cultures (Hueppe's method) give good 

 growths. Passing currents of air increase the growth; on 

 agar, growth is slow. 



Colonies on Agar Plates. At 24 C. little round colonies, 

 white under low power, granular center; irregular borders. 



Stab-cultures. Small, white drops along the needle-track. 

 In glycerin-agar a somewhat profuse growth. Media should 

 be slightly acid. 



Potato. On alkaline surface, a grayish layer in forty-eight 

 hours. 



