THE PITCHER LIQUOR OF NEPENTHES. 



123 



in lo c.c. of the sterile suspension of protein. In one series of eight 

 experiments, indol had not been produced after incubation for ten 

 days. In another series of eight experiments, neither free trypto- 

 phane nor indol was present after incubation for twelve days. 



Digestion of Proteins by the Bacteria. — The proteins used were : 

 casein, egg albumen, unswollen carmine fibrin, edestin, ricin (Ja- 

 coby), protein (prepared from aleuronat). The media were pre- 

 pared by addition of 2 per cent, of agar and approximately i per 

 cent, of one of the proteins to the stock solution of inorganic salts, 

 and were then sterilized. The proteins, therefore, served as the 

 sole source of carbon and nitrogen for the bacteria. These media 

 were used in plating experiments, sowing i c.c. of pitcher liquor 

 in each plate. Whenever proteolytic bacteria were present in the 

 pitcher liquor, their colonies gradually digested and dissolved the 

 suspended particles of protein over which they grew. The plates 

 were examined at intervals until drying of the media rendered 

 further observation useless. The bacteria grew and colonies de- 

 veloped on the vast majority of the plates, as may be seen by refer- 

 ence to Table VII., which gives certain details of these experiments. 



TABLE VII. 



Digestion of Protein Media by Bacteria, Present in Liquor 

 OF Open Pitchers. 



Protein Used. 



Digestion 

 Begun Be- 

 tween Days. 



Total Period 

 of Incuba- 

 tion Days. 



Casein 



Egg albumen 



Carmine fibrin 



Edestin 



Ricin 



Protein (from aleuronat) 



3 to 5 



5 to 9 



3 to 9 



By 9th day 



3 to 5 



12 to 14 

 9 



The suspended tgg albumen was not even partially digested ; possi- 

 bly this was due to the presence of non-coagulable ovomucoid, and 

 its utilization by the bacteria as a source of carbon and nitrogen. 

 The other suspended proteins were gradually digested, the digestion 

 becoming more marked as the period of incubation increased ; how- 

 ever, complete digestion and disappearance of the suspended parti- 

 cles had never occurred by the end of this period. 



