454 HEPBURN AND ST. JOHN— BIOCHEMICAL STUDIES 



Action on Special Media 



After the plates of the special media had been inoculated, they were 

 held in an incubator at 37°C., and were examined at intervals as stated 

 below, until drying of the media rendered further observation useless. 



Casein agar. Eight experiments were made using this medium. In 

 seven experiments, growth, but no proteolysis, had occurred at the end 

 of 3 days; digestion of the casein had begun by the fifth day, had become 

 more marked by the ninth day, and still more marked by the twelfth 

 day. In the eighth experiment, bacterial colonies failed to develop. 



Egg albumen agar. Two series of experiments were made with egg 

 albumen agar as the substrate. The first series included eight experi- 

 ments; colonies had appeared in three experiments by the third day 

 and in a fourth experiment by the ninth day. The plates in the other 

 experiments remained sterile. Digestion of the albumen was not noted, 

 even at the end of 12 days. 



In a second series, which consisted of seven experiments, growth of 

 the bacteria occurred during the first five days of incubation, but pro- 

 teolysis of the albumen had failed to develop at the end of 14 days. 

 Possibly, in both series, sufficient ovomucoid (a non-coagulable protein) 

 was present in the dried egg albumen to supply the bacteria with the 

 necessary carbon and nitrogen. 



Carmine fibrin agar. Six experiments were conducted on carmine 

 fibrin agar. Washed, unswoUen carmine fibrin had been used in the 

 preparation of the medium, and the flocks were rather large. Colonies 

 developed by the third day, and showed a marked tendency to grow over 

 the flocks. Proteolysis had not become apparent on the fifth day. On 

 the ninth day digestion of the fibrin was distinctly under way. 



Edestin agar served as the medium in four experiments. Growth of 

 the bacteria, and possibly incipient proteolysis of the edestin, occurred 

 by the third day. No further change was noted on the fifth day. The 

 digestion of the edestin had advanced somewhat by the ninth day, and 

 was still more marked on the twelfth day. 



Ricin agar was used as the medium in three experiments. Colonies 

 developed in one experiment by the third day, and in another experi- 

 ment by the fifth day. Digestion of the ricin had begun in both 

 experiments by the ninth day, and had become very marked by the 

 twelfth day. Bacterial growth failed to occur in the third experiment. 



Protein agar. Agar, containing protein from aleuronat, served as 

 the medium in eight experiments. On the third day colonies were pres- 

 ent in all the experiments, and proteolysis had probably begun in six 



