35 2 Suppuration 



Colonies. Upon gelatin plates very small, colorless, trans- 

 lucent colonies appear in from twenty-four to forty-eight 

 hours. When superficial, they spread out to form flat disks 

 about 0.5 mm. in diameter. The microscope shows them to 

 be irregular and granular, to have a slightly yellowish color 

 by transmitted light, and to have numerous irregularities 

 around the edges, due to projecting chains of the cocci. No 

 liquefaction of the gelatin occurs. 



Gelatin Punctures. In gelatin puncture cultures no 

 liquefaction is observed. The minute spheric colonies grow 



Fig. 106. Streptococcus colonies on serum agar (From Hiss and Zins- 

 ser, ' Text-Book of Bacteriology," D. Appleton & Co., Publishers). 



along the whole length of the puncture and form a slightly 

 opaque granular line. 



Agar-agar. Upon agar-agar an exceedingly delicate 

 transparent growth develops slowly along the line of inocu- 

 lation. It consists of small, colorless, or slightly grayish 

 transparent colonies which do not readily coalesce. 



Blood-serum. The growth upon blood-serum resembles 

 that upon agar-agar. The colonies are small, white, dis- 

 crete, and do not affect the medium. 



Potato. The streptococcus does not seem to grow well 

 upon potato, the colonies being invisible. 



Bouillon. In bouillon the cocci develop slowly, seeming 

 to prefer a neutral or feebly alkaline reaction. The medium 

 remains clear, while numerous small flocculi are suspended 

 in it, sometimes adhering to the sides of the tube, sometimes 

 forming a sediment. When the flocculi formation is distinct, 

 the name Streptococcus conglomerate (Kurth) is sometimes 

 given to the organism ; when the medium is diffusely clouded, 

 it is called Streptococcus dijjusus. 



