PATHOGENIC BACTERIA. 89 



the size of a red corpuscle's diameter, their ends rounded, usu- 

 ally solitary, often, however, lying in pairs in such a manner as 

 to form an acute angle. Sometimes they are ' S'-shaped. In 

 colored preparations little oval spaces are seen in the rod, which 

 resemble spores ; but the question of the existence of spores is 

 still undecided. 



Properties. Does not possess self-movement. 



Growt h. Requires special media for its growth, and a temper- 

 ature varying but slightly from 37.5 C. It grows slowly, de- 

 veloping first after ten days, reaching its maximum in throe 

 weeks. It is facultative anaerobic. On gelatine it does not 

 form a growth. 



Colonies on Mood 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 Ayar. 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 FIG. 47. 



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 ruga? of the stomach, and some- ^ 



times looks like crumbs of bread moist- 

 ened. The impression or "Klatsch" preparation shows under 



