352 MANUAL OF BACTERIOLOGY. 



But after it becomes accustomed to the artificial environment, 

 it may be readily cultivated on a number of different media, 

 though its growth is always relatively slow as compared with 

 that of many other bacteria. It does not grow at a tempera- 

 ture below 29 C., and the best temperature is around 38 C. It 

 cannot, therefore, be cultivated upon gelatin even if this were a 

 suitable medium otherwise. It grows well upon blood-serum, 

 where the growth becomes visible in from ten to fourteen days in 



.-*. 







FIG. 92. Bacillus tuberculosis in sputum, stained with carbol-fuchsin and 

 methylene-blue. Photomicrograph in two colors. (X 1000.) 



the incubator. It forms a dry, mealy, scaly mass, elevated above 

 the surface, of a grayish-brown color. It also grows upon 

 glycerin- agar; or glycerin-bouillon, on which it forms a pel- 

 licle; upon potato; upon milk containing i per cent, of agar 

 and upon coagulated egg (see page 76). It is important to 

 have the medium moist. It can be cultivated from tuberculous 

 sputum only with great difficulty. It is best to obtain it from 

 the tissues of an animal that has died of tuberculosis, where the 



