220 PA THOGENIC BA CTERIA. 



Pawlowski was able to cultivate the bacillus upon 

 potato, but Sander, who found that it could be readily 

 grown upon various vegetable compounds, especially 

 upon acid potato mixed with glycerin, also found that 

 upon such compounds its virulence was constantly lost. 



It has also been shown that the continued cultivation 

 of the tubercle bacillus upon such culture-media as 

 are appropriate so lessens its parasitic nature that in the 



FIG. 63. Bacillus tuberculosis : adhesive cover-glass preparation from a fourteen- 

 day-old blood- serum culture; x loo (Frankel and Pfeiffer). 



course of time it can be induced to grow feebly upon the 

 ordinary agar-agar. 



It is really surprising to note the extremely simple 

 compounds in which the tubercle bacillus can be grown. 

 Instead of requiring the most concentrated albuminous 

 media, as was once supposed, Proskauer and Beck have 

 shown that the organism can grow in non-albuminous 

 media containing asparagin, and that it can even be in- 

 duced to grow upon a mixture of commercial ammonium 

 carbonate, 0.35 per cent.; primary potassium phosphate, 

 0.15 per cent.; magnesium sulphate, 0.25 per cent.; 

 glycerin, 1.5 percent. It was even found that tuberculin 

 was produced in this inorganic mixture. 



