BACILLUS (EDEMAT1S. 



525 



In tubes containing about 20 to 30 c.c. 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 FIG. 90. 



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. 90.) 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 accom- 

 panied by the production gas-bubbles. 



It causes rapid liquefaction of blood- 

 serum, with production of gas-bubbles, 

 and in two or three days the entire 

 medium may have become converted 

 into a yellowish, semifluid mass. 



The most satisfactory results in the 

 study of the colonies are obtained by 

 the use of plates of nutrient agar-agar tin culture. (After 



. . - . . I'lii FRANKKI, and PFEIF- 



kepfc in a chamber in which all oxygen FER>) 

 has been replaced by hydrogen. The colonies appear as 

 dull whittish points, irregular in outline, and when viewed 

 with a low-power lens are seen to be marked by a net- 



colonies of the ba- 



