Cultivation 415 



fragments slowly sedimenting and forming a miniature snow-storm 

 in the flask or tube. The organism at times also causes a diffuse 

 cloudiness of the medium, but, not being motile, soon settles to the 

 bottom in the form of a flocculent precipitate which has a tendency 

 to cling to the sides of the glass, and leave the bouillon clear. 



No fermentation occurs in bouillon to which sugar is added, though 

 acids are soon formed by which the growth is checked. If, how- 

 ever, the quantity of sugar be too small to check the growth, the 

 acidity gives place to increasing alkalinity at a later period. 



Fig. 157. — Bacillus diphtherise; colony twenty-four hours old, upon agar-agar 

 Xioo (Frankel and Pfeififer). 



Spronck* found that the characteristics of the growth of the 

 diphtheria bacillus in bouillon, as well as the amount of toxin 

 produced, vary according to the amount of glucose in the bouillon. 



Zinnof found that digested brain added to the culture bouillon 

 greatly facilitated the growth of diphtheria and tetanus bacilli and 

 increased the toxin-production. 



Blood-serum. — The bacillus grows similarly upon blood-serum 

 and Loffler's mixture, but more luxuriously upon the latter, where 

 large, creamy-white, discrete and confluent, moist, shining colonies 

 form. The rapidity of the growth which is abundant in twenty- 

 four hours, and the appearances presented are quite characteristic. 



Loffler has shown that the addition of a small amount of glucose 

 to the culture-medium increases the rapidity of growth, and suggests 

 a special medium which bears his name — Lofiier's blood-serum 

 mixture: 



Blood-serum 3 



* (( 



Ordinary bouillon -j- i per cent, of glucose 1 



, "Ann. de I'Inst. Pasteur," Oct. 25, 1895, vol. ix. No. 10, p. 758. 

 T Centralbl. f. Bakt.," Jan. 4, 1902, xxxi. No. 2, p. 42. 



