GENUS BACTERIUM 249 



accustomed to artificial cultivation. It is not readily obtained 

 in pure culture from tuberculous tissues. Smith 12 found that 

 by inoculating guinea pigs with the suspected material and 

 as soon as the disease had begun to develop chloroforming the 

 pigs and transferring quite large pieces of the diseased organs, 

 such as spleen or liver, directly to the surface of dog serum 

 (coagulated at 72 C.) and placing them in an incubator at 

 37.5 C. in which there was considerable moisture, the multi- 

 plication of the organisms continues and in some days visible 

 growth appears on the serum at the edges of the tissues. Some 



57. Cultures of tubercle bacteria in flasks on glycerinated 

 bouillon. 



workers have little difficulty in the use of the ordinary beef 

 serum. 



Blood serum. On blood serum at 37.5 C., colonies usu- 

 ally become visible at the end of eight to fourteen days. They 

 appear at first as small, dry, grayish-white, scaly spots with 

 corrugated surfaces. After three or four weeks' cultivation, 

 these join together, covering the surface of the medium as a 

 dry, whitish, wrinkled membrane. Coagulated dog serum is 

 regarded by Theobald Smith 13 as one of the most favorable 

 media for the growth of tubercle bacteria. 



12 Smith, loc. cit. 



13 Th. Smith. Jour. Exp. Med., Vol. Ill (1898) p. 451. 



