THE TUBERCLE BACILLUS 



485 



bottom. In old cultures, the membrane assumes a yellowish hue. 

 These cultures emit a peculiar aromatic odor. 



Glycerin potato forms a favorable culture medium for the bacillus. 



Hesse ^ has devised a mediimi containing a proprietary preparation 

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

 proliferate more rapidly than other bacteria. His method has yielded 

 excellent results in the hands of other 

 observers, both in isolation and in 

 rapid cultivation. It is prepared as 

 follows : 



•'Nahrstoff Heyden" '.... 



Sodium chloride 



Glycerin 



Agar 



Normal sodium solution. . 



10 grams 



5 " 



30 " 



10 " 



5 CO. 



Aq. dest 1,000 " 



A variety of other culture media 

 have been devised, none of them, how- 

 ever, possessing any marked advan- 

 tages over those given. 



Biological Considerations. — The 

 tubercle bacillus is markedly depend- 

 ent upon the free access of oxygen. 

 The optimum temperature for its de- 

 velopment is 37.5° C. Temperatures 

 below 30° and above 42° C. inhibit 

 its growth. In fluid media, the bacilli 

 are killed by^a temperature of 60° in 

 fifteen to twenty minutes, by one of 80° 

 in five minutes, by one of 90° in one 

 to two minutes. They will withstand 



dry heat at 100° C. for one hour. They are resistant to cold. The 

 comparatively high powers of resistance of the bacillus are attributed 

 to the protective qualities of the waxy cell membrane.' 



The natural life of cultures, kept in favorable environment, is from 



' Hesse, Zeit. f. Hyg., xxxi. 



^ "Nahrstoff Heyden" ia prepared in Germany. It is a white powder similar 

 to nutrose. 



' Th. Smith, Jour.Exper. Med., 1899; Grancher et Ledoux-Lebard, Arch, de mM. 

 expgr., 1892; Galtier, Compt. rend, de I'acad. des sci., 1887. 



Fig. 104. — CuM'TmE of Bacillus 

 Tuberculosis in Flask of Glyc- 

 erin Bouillon. 



