PATHOGENIC BACTERIA. 



99 



FIG. 52. 



Colonies on Blood Serum. Koch first used blood serum for 

 culture ground, and obtained thereon very good growths. Test- 

 tubes with stroke culture were placed in the brood oven at 37 C. 

 for ten to fourteen days, when small glistening white points ap- 

 peared which then coalesced to form a dry, white, scale-like 

 growth. Under microscope composed of many fine lines con- 

 taining the tubercle bacillus. 



Glycerine Agar.J$y adding four to six per cent, glycerine to 

 ordinary agar-peptone medium, Nocard and Roux obtained a- 

 culture ground upon which tubercle bacilli grew much better 

 than upon blood serum. This is now almost exclusively used. 



Stroke cultures are here used as with blood serum. They are 

 placed in brood-oven after inoculation, and remain there about 

 ten days, at a temperature of 37 C. 

 The cotton plugs of the tubes are 

 covered with rubber caps, the cotton 

 first having been passed through the 

 flame, and moistened with a few drops 

 of sublimate solution. The rubber 

 cap prevents the evaporation of the 

 water of condensation which always 

 forms, and keeps the culture from dry- 

 ing up. 



The growth which occurs resembles 

 the rusee of the stomach, and some- jj r ff 500 x ' < F nkel and 

 times looks like crumbs of bread moist- 

 ened. The impression, or "Klatsch" preparation shows under 

 the microscope a thick curled-up centre around which threads 

 are wound in all directions. And these fine lines show the 

 bacilli in profusion. 



Potato. It can be cultivated on slices of potato which are 

 placed in air-tight test-tubes. 



Bouillon. Bouillon containing four per cent, glycerine is a 

 veT good nurture ground. 



Varieties. Branching and other aberrant forms are not rare, 

 and the tendency now is to class the organism with the " higher 

 bacteria." Other acid-fast bacilli exhibit similar types and it is 



Tubercle bacilli in human 



