THE TUBERCLE BACILLUS 485 



teria is collected in a wide-mouthed bottle and an equal volume of normal 

 sodium hydroxid is added. This is shaken and left in the incubator for three 

 hours, shaking every half hour. It. is then neutralized to litmus with normal 

 hydrochloric, centrifugalized, and the sediment planted. 



On blood serum at 37.5 C., colonies become visible at the end of 

 eight to fourteen days. They appear as small, dry, scaly spots with 

 corrugated surfaces. After three or four weeks, these join, covering 

 the surface as a dry, whitish, wrinkled membrane. Coagulated dog 

 serum is regarded by Theobald Smith * as a favorable media for the 

 growth of tubercle bacilli. 



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-agar (gly- 

 cerin 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%, glycerin six 

 per cent, slightly alkaline) is a favorable medium. It should be filled, 

 in shallow layers, into wide-mouthed flasks, since oxygen is essential. 

 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. 



Glycerin potato forms a favorable culture medium for the bacillus. 



Hesse 2 has devised a medium containing a proprietary preparation 

 known as "Nahrstoff Hey den, " upon which tubercle bacilli are said to 

 proliferate more rapidly than other bacteria. His method has yielded 

 excellent results. It is prepared as follows: 



"Nahrstoff Heyden" 3 10 grams 



Sodium chlorid 5 " 



Glycerin. . .. 30 " 



Agar ! 10 " 



Normal sodium solution 5 c.c. 



Aq. dest 1,000 " 



1 Th. Smith, Jour. Exp. Med., iii, 1898. 



2 Hesse, Zeit. f. Hyg., xxxi. 3 "Nahrstoff Heydeu" is prepared in Germanyf 

 It is a white powder similar to nutrose. 



