3° 6 



PATHOGENIC BACTERIA. 



changes are necessary, three or four washings being 

 sufficient. 



In 1887, Nocard and Roux gave a great impetus to 

 investigations upon tuberculosis by their discovery that 



the addition of 4-8 per cent, 

 of glycerin to bouillon and 

 agar-agar made them suitable 

 for the development of the 

 bacillus, and that a much 

 more luxuriant development 

 could be obtained upon these 

 media than upon blood-se- 

 rum. The growth upon such 

 "glycerin agar-agar" (Fig. 

 67) very much resembles 

 that upon blood-serum. The 

 growth upon bouillon with 

 4 per cent, of glycerin is 

 also luxuriant. A critical study 

 of the relationship of massive 

 development and glycerin was 

 made by Kimla, Poupe, and 

 Vesely, 1 who found that the 

 most luxuriant growth occurred 

 when the culture-media con- 

 tained from 5 to 7 per cent, of glycerin. As tubercle 

 bacilli require considerable oxygen for their proper de- 

 velopment, they grow only upon the surface of the bouil- 

 lon, where a thick wrinkled surface growth forms. This 

 growth is rather brittle, and after a time subsides. 



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 is disadvantageous. 

 Pawlowski was able to cultivate the bacillus upon 

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

 grown upon various vegetable compounds, especially 



1 Revue de la Tuberculose, 1898, vi., p. 25. 



Fig. 67. — Bacillus tuberculosis on 

 "glycerin agar-agar." 



