726 Tuberculosis 



Non-albuminous Media. Instead of requiring the most 

 concentrated albuminous media, as was once supposed, 

 Proskauer and Beck* have shown that the organism can be 

 made to grow in non-albuminous media containing asparagin, 

 and that it can even be induced 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 per cent. Tuberculin was pro- 

 duced in this mixture. 



Gelatin. The tubercle bacillus can be grown in gelatin 

 to which glycerin has been added, but as its development 

 takes place only at 37 to 38 C., a temperature at which 

 gelatin is always liquid, its use for the purpose has no 

 advantages. 



Fig. 243. Bacillus tuberculosis: a, Source, human; b, source, bovine. 

 Mature colonies on glycerin-agar. Actual size (Swithinbank and 

 Newman) . 



Appearance of the Cultures. Irrespective of the media 

 upon which they are grown, cultures of the tubercle bacil- 

 lus present certain characteristics which serve to separate 

 them from the majority of other organisms, though insuffi- 

 cient to enable one to certainly recognize them. 



The bacterial masses make their appearance very slowly. 

 As a rule very little growth can be observed at the end of a 

 week, and sometimes a month must elapse before the cul- 

 tures can be described as well grown. 



They usually develop more rapidly upon fluid than upon 

 solid media. The growth is invariably and purely aerobic, 



* "Zeitschrift fur Hygiene," Aug. 10, 1894, xvm, No. i. 



