2OO GARY N. CALKINS. 



this organism, therefore, forms the staple article of diet for Para- 

 mcecium in culture. In the body of the infusorian the bacteria 

 are collected in the usual gastric vacuoles where the first stages, 

 at least, of digestion are carried on. No one has identified the 

 proteolytic ferment which is active in this process. The work of 

 Meissner, LeDantec, Fabre-Domergue, Greenwood and others 

 has shown that something analogous to pepsin plays the most 

 important role in the process, but nothing definite concerning the 

 ferment is known. In an allied group, however, the Rhizopoda, 

 some work has recently been done which may throw light upon 

 the digestive processes of the Infusoria. H. Mouton, 1 working 

 in Metschnikoff s laboratory, has succeeded in extracting the 

 proteolytic ferment from a bacillus-eating Ainaba. Tests ot 

 various kinds showed that the ferment is more like trypsin in its 

 action than like pepsin, and Mouton comes to the conclusion 

 that it is intermediate between the two. As the foods of this 

 Aniffba and of Paramoeciuin are probably similar in proteid com- 

 position, it is not improbable that the proteolytic ferments are 

 much alike. 



Whether or not the proteolytic ferment in Paramcecium is the 

 same as that in Amoeba, there is no doubt that some such active 

 agent is operative in the digestive processes of our infusorian. 

 Furthermore, there is a certain amount of evidence to indicate 

 that it is this ferment-forming power that becomes weakened in 

 the protoplasm of Paranuvciuni as the race grows older. Phy- 

 siological "degeneration" is not due, as Maupas supposed, to 

 the loss of some of the necessary organs of the cell through 

 degeneration, nor is it due to inability to take food, for, when in 

 the depressed condition, the ParauuTcimn still maintains a cur- 

 rent of bacteria into the mouth -opening, and food vacuoles are 

 still formed. Frequently when in this condition the organisms 

 appear black because of the undigested food balls, a fact which 

 indicates that it is the digestive function that wears out. In this 

 connection it is interesting to note the effect of dilute alcohol on 

 the general metabolism of Paramcccinni. Mr. C. C. Lieb, work- 



1 H. Mouton. Recherches sur la digestion chez les Amibes et sur leur diastase in- 

 tracellulaire. Thesis presented at the Faculte de sciences de Paris, 1902. Reprint 

 pp. I -60. 



