Isolation and Cultivation 



319 



stood inside, so that the atmosphere may be constantly 

 saturated with moisture. The tubes are inoculated with 

 bits of tissue the size of a small pea, torn from the tubercu- 

 lous foci. The fragments of tissue 

 are not crushed or comminuted, but 

 are simply laid upon the undis- 

 turbed surface of the blood-serum 

 and then incubated for several 

 weeks. If no growth is apparent 

 after this period, the bit of tissue 

 is stirred about a little and the 

 tube returned to the incubator, 

 where growth almost immediately 

 begins from bacilli scattered over 

 the surface as the bit of tissue was 

 moved about. 



Smith secures the tubercle bacil- 

 lus from sputum by intraperitoneal 

 inoculation of a guinea-pig, and 

 prefers metastatic tuberculous foci 

 to local foci of disease from which 

 to secure material for inoculation. 

 The guinea-pig should not be al- 

 lowed to die, but should be chloro- 

 formed at the end of the third week. 



Gelatin. The tubercle bacillus 

 can be grown in gelatin to which 

 glycerin has been added, but as its 

 development takes place only at 

 37-38 C., a temperature at which 

 gelatin is always liquid, its use for 

 the purpose has no advantages. 



Potato. Pawlowski * was able to 

 isolate the bacillus upon potato, but 

 Sander, who found that it could 

 be readily grown upon various vege- 

 table compounds, especially upon 

 acid potato mixed with glycerin, 

 also found that upon such com- 

 pounds its virulence was lost, and 

 Rosenau f has shown that it can 



* "Ann. de 1'Inst. Pasteur," 1888, t. vi. 

 f'Jour. Amer. Med. Assoc.," 1902. 



Fig. 94. Bacillus tu- 

 berculosis; glycerin agar- 

 agar culture, several 

 months old (Curtis) 



