524 



BACTERIOLOGY. 



Fig. £ 



an atmosphere of hydrogen. It causes liquefaction of 



gelatin. 



In tubes containing about 20 to 30 c.o. of gelatin 

 that has been liquefied, inoculated with 

 a small amount of the culture, and 

 then rapidly solidified in ice-water, 

 growth appears in the form of isolated 

 colonies at or near the bottom of the 

 tube in from two to three days at 

 20° C. These colonies, when of from 

 0.5 to 1 mm. in diameter, appear as 

 spheres filled with clear liquid, and 

 are difficult, for this reason, to detect. 

 (Fig. 99.) As they gradually increase 

 in size the contents of the spheres be- 

 come cloudy and marked by fine radi- 

 ating stripes, easily to be detected with 

 the aid of a small hand-lens. In deep 

 stab-cultures in agar-agar and in gela- 

 tin development occurs only along the 

 track of puncture, at a distance below 

 the surface. Growth is frequently ac- 

 companied by the production of gas- 

 bubbles. 



It causes rapid liquefaction of blood- 

 serum, with production of gas-bubbles, 

 and in t^^■o or three days the entire 

 medium may have become converted 

 into a yellowish, semi-fluid mass. 



The most satisfactory results in the 

 study of the colonies are obtained by 



the use of plates of nutrient agar-agar kept in a chamber 



in which all oxygen has been replaced by hydrogen. 



Colonies of the ba- 

 cillus of malignant 

 oedema in deep gela- 

 tin culture. (After 

 FrXnicel and Pfeif- 



FER.) 



