GENERAL PHYSIOLOGY 



1S9 



Kriikenberg (1886) from the Mycetozoon /Eihalium septicum, and 

 by Hartog and Dixon (1893) from the amoeba Pelomyxa palustris, 

 while Metschnikoff (1889) showed that the food vacuoles in the 

 Plasmodia of Mihalium have an acid reaction favorable to the activ- 

 ity of such ferments. Trypsin-like ferments have likewise been 

 isolated by Mouton (1902), from soil amoeba cultivated in large 

 numbers on agar; also diastatic ferments were easily obtained from 

 Bcdantidium coli by Glaessner (1908), and from Pelomyxa palustris 

 by Hartog and Dixon (1893). 



The typical course of a gastric \'acuole through the endoplasm of 

 ciliates has been carefully worked out by Greenwood and by 



Fig. 92. — Carchcsium polypinum ? History of food vacuole; (a) stage of .storage 

 and little change; (b) .stage of acid reaction; (c) neutral reaction. (After Green- 

 wood.) 



Nirenstein for Carchcsium and Paramecium caudatum (Fig. 92). 

 Prowazek (1897) staining with neutral red found a collection of 

 red granules about the gastric vacuole; similar granules were 

 observed by him and by Nirenstein (1905) to pass into the gastric 

 vacuole and to mix with the food substances from which circum- 

 stance they were regarded by both observers as the bearers of 

 ferments (trypsin-like according to Nirenstein). The so-called 

 Excretperlen (excretory granules) first described by Prowazek 

 (1897) and interpreted by him, by Nirenstein and by Doflein (1916) 

 as furnishing evidence of excretion through the general cell mem- 

 brane, may be with equal justification interpreted as secretory 



