362 Tuberculosis 



grow upon almost any cooked and glycerinized vegetable 

 tissue. According to French writers, the virulence of the 

 bacillus is not diminished when it grows upon potato. It 

 has also been said that the continued cultivation of the 

 tubercle bacillus upon culture media lessens its parasitic 

 nature, so that in the course of time it can be induced to 

 grow feebly upon the ordinary agar-agar, and that pro- 

 longed cultivation destroys its virulence. 



Egg Media. Dorset * recommends the isolation of the 

 tubercle bacillus upon an egg medium, which has the ad- 

 vantage of being cheap and easily prepared, while eggs are 





Fig. 109. Bacillus tuberculosis ; adhesive cover- glass preparation 

 from a fourteen-day-old blood-serum culture X 100 (Frankel and 

 Pfeiffer). 



always at hand, and can be made into an appropriate 

 medium in an hour or two. He also claims that the chemic 

 composition of the eggs makes them particularly adapted 

 for the purpose. The medium is prepared by carefully 

 opening the egg and dropping its contents into a wide- 

 mouth sterile receptacle. The yolk is broken with a sterile 

 wire and thoroughly mixed with the white by gentle shaking. 

 The mixture is then poured into sterile tubes, about 10 c.c. 

 in each, inclined in a blood-serum sterilizer, and sterilized 

 and coagulated at 70 C. for two days, the temperature 

 * " American Medicine," 1902, vol. in, p. 555. 



