Bouillon 433 



Bouillon. — When planted in bouillon a distinct, whitish, granular 

 pellicle forms upon the surface of the clear medium. The pellicle 

 appears quite uniform when the tube or flask is undisturbed, but it 

 is so brittle that it at once falls to pieces if disturbed, the minute 

 fragments slowly sedimenting and forming a miniature snow-storm 

 in the flask or tube. When dextrose is added to the bouillon the 

 organism causes a diffuse cloudiness of the medium, but, not being 

 motile, soon settles to the bottom in the form of a flocculent precipi- 



Fig. 156. — Bacillus diphtheria; colony twenty-four hours old, upon agar-agar 

 Xioo (Frankel and Pfeiffer). 



tate 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. 



Blood-serum. — Thfe bacillus grows upon blood-serum. 



LoflSer* 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 — Loffler's blood-serum 

 mixture: 



Blood-serum (of sheep or calf) 3 



Ordinary bouillon -|- i per cent, of glucose i 



This mixture is filled into tubes, coagulated, and sterilized like 

 blood-serum, and is one of the best known media to be used in con- 

 nection with the study of diphtheria. 



Material from the infected throat can be taken with a swab or 

 platinum loop and spread upon the surface of several successive 

 tubes of Loffler's blood-serum media. Upon the first a confluent 



* "Mitt. a. d. Kais.-gesundheitsamt," 1S84, IL 

 28 



