2 PRACTICAL BACTERIOLOGY. 



Examine these tubes at the end of 24 and 48 hours. 

 Growth is more rapid at the higher temperature, but 

 the pigmentation is slight, while a more slowly appearing 

 growth, deeply pigmented, is noted in the other tube. 



Pigmentation is in nearly all chromogenic species, 

 more marked at the lower temperature than at the 

 higher. 



2. Make a gelatine slope culture of Bacillus cyano- 

 genus and place in the incubator at 20°C. 



Examine each day and note the gradual intensifica- 

 tion of the pigmentation of the media, the growth itself 

 being uncolored. 



3. Make two potato tube cultures of Bacillus ruber. 

 Keep one exposed freely to light in the room, and 



place the second in the incubator (dark) at 20°C. 

 Growth and pigmentation will be more marked in the 

 latter tube. 



4. Make gelatine stab cultures of (a) Bacillus 

 pyocyaneus, (b) Staphylococcus pyogenes aureus, (c) 

 Sarcina lutea. 



Incubate at 20*^0 and examine daily. These bacteria 

 liquefy gelatine more or less rapidly. 



5. Make broth cultures of (a) Torula rosea and (b) 

 Bacillus proteus mirabilis. Place in incubator at 20°C. 



6. Make gelatine slope cultures of (a) Staphylococ- 

 cus cereus flavus, (b) Streptococcus pyogenes. Keep 

 in incubator at 20°C. 



