212 MICROBIOLOGY 



Agar. On agar, after 24 hours, a white glistening granu- 

 lar growth of confluent colonies appears. It reaches its maxi- 

 mum growth on the fourth day with a somewhat granular 

 surface and irregular wavy margin. On agar plates these 

 appear as smooth, whitish, flatly convex, ceraceous colonies, 

 about 1.5 mm. in diameter. By transmitted light, they present 

 a whitish center and a pearly margin. Colonies in the depth 

 of the agar are slightly brownish with an irregular outline. 

 They may be either round or lentil shaped but are always 

 minute. There is no distinguishing difference in the growth 

 of this organism on glycerin or on serum gelatin agar. 



Gelatin. It grows somewhat slowly in gelatin, evidences 

 of growth not appearing until the second day. The colonies 

 are more minute than on agar and the growth that appears on 

 the surface, though similar in consistency, is likewise thinner 

 and less profuse than on agar. It does not liquefy gelatin 

 until several generations have been grown on artificial media. 

 With cultures that have been passed through several genera- 

 tions, the surface growth in the tube cultures on the fourth or 

 fifth day begins to sink in the medium, after which liquefac- 

 tion is very rapid, and within two or three days it may reach 

 the bottom of the tube. The surrounding gelatin is then at- 

 tacked and the whole mass becomes fluid with a white pellicle 

 on the surface. In gelatin plates, liquefaction does not begin 

 until the fourth or fifth day and sometimes later. 



Potato. On this medium, inoculated from a vigorous 

 bouillon culture, growth is somewhat feeble and ceases on the 

 third day. 



Blood serum. On dog serum, the organism forms a nar- 

 row compact line of whitish color with edges slightly elevated 

 above the level of the body of the growth. The water of con- 

 densation becomes clouded. After 7 or 8 days, the color as- 

 sumes a brownish tint. 



Bouillon. In bouillon at 37 C. the liquid becomes cloudy 

 after 10 hours, and continues to increase for about 24 hours. 

 At this time there may be a deposit of organisms at the bot- 

 tom of the tube. The sediment is pearl gray in color and upon 



