592 



PATHOGENIC MICROORGANISMS 



Slants of agar, to which whole rabbit's blood has been added in quan- 

 tities of from 1 to 2 c.c. to each tube, make an excellent medium. 



Cultivation methods were simplified by the discovery by Roux and 

 Nocard that glycerin facilitates cultivation. Upon glycerin-cigar 

 (glycerin 3 to 6 per cent), at 37.5 C., colonies become visible at the end 

 of from ten days to two weeks. 



Glycerin bouillon (made of beef or veal with pepton 1 per cent, 



glycerin 6 per cent, slightly alkaline) 

 is a favorable medium. It should be 

 filled, in shallow layers, into wide- 

 mouthed flasks, since oxygen is essen- 

 tial. Transplants to this medium should 

 be made by carefully floating flakes of 

 the culture upon the surface. In this 

 medium the bacilli will spread out 

 upon the surface, at first as a thin, 

 opaque, floating membrane. This 

 rapidly thickens into a white, wrinkled, 

 or granular layer, spreading over the 

 entire surface of the fluid in from four 

 to six weeks. Later, portions of the 

 membrane sink. In old cultures, the 

 membrane becomes yellowish. These 

 cultures emit a peculiar aromatic 

 odor. Cultures when first grown on 

 solid media are a little difficult to start 

 on glycerin broth. To accomplish this 

 it is best to grew them for a few 

 weeks on egg or glycerin egg slants 

 containing considerable amounts of 

 condensation water. At the end of 

 this time the growth will have begun 



to grow over the surface of the condensation water, and from this 

 pellicle a bit can be picked up with a bent loop, carefully removed with- 

 out allowing it to immerse in the fluid and this carefully floated on the 

 surface of the glycerin broth in the flask. 



Glycerin potato forms a favorable culture medium for the bacillus. 

 Hesse 19 has devised a medium containing a proprietary preparation 



FIG. 64. CULTURE OF BACILLUS 

 TUBERCULOSIS IN FLASK OF 

 GLYCERIN BOUILLON. 



18 Hesse, Zeit. f. Hyg.. xxxi. 



