396 



PATHOGENIC BACTERIA. 



thoueh sometimes indented borders. Under the micro- 

 scope they appear as granular, yellowish-brown colonies 

 with irregular borders (Fig. 86). 



When planted in bouillon the organism sometimes 

 causes a diffuse cloudiness at first, but, not being motile, 

 soon settles to the bottom in the form of a rather floccu- 

 lent precipitate which has a tendency to cling to the sides 

 of the glass, but leaves the bouillon clear. Sometimes 

 a delicate pellicle of granular appearance forms upon 



Fig. 86. — Bacillus diphtheria?, colony twenty-four hours old upon agar-agar; 

 x ioo (Frankel and Pfeiffer). 



the surface, especially when the cultivation is made by 

 the method of Fernbach with a passing current of air. 

 This mycoderma, which may appear quite regular when 

 the flask is undisturbed, is so brittle that it at once falls 

 to pieces if the flask be moved, the minute fragments 

 forming a miniature snow-storm in the tube. 



Spronck 1 has determined that the characteristics of 

 the growth of the diphtheria bacillus in bouillon, as well 

 as the amount of toxin-production, vary according to the 

 amount of gducose in the bouillon. He divides the cult- 

 ures into three types : 



1 Annales de f Inst. Pasteur, October 25, 1895, vol. ix., No. 10, p. 758. 



