PATHOGENIC BACTERIA III 



growth. Under microscope composed of many fine lines con- 

 taining the tubercle bacillus. 



Glycerin-agar. By adding 4 to 6 per cent, glycerin to 

 ordinary agar-peptone medium, Nocard and Roux obtained a 

 culture-media upon which tubercle bacilli grow 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 incubator 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 



Fig. 58. Giant-cell containing bacilli (from a photograph made by Dr. Wm. 

 M. Gray). 



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 drying up. 



The growth which occurs resembles the rugae of the stomach, 

 and sometimes looks like moistened crumbs of bread. The 

 impression or "Klatsch" preparation shows under the micro- 

 scope a thick, curled-up center 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. 



