SOME PROBLEMS IN THE PHYSIOLOGY OF THE PROTOZOA 287 



crystals in Metazoa (Stein, '59; Wrzesniowski, '79; Entz, '79; Maupas, 

 '83; Rhumbler, '88), while from the form of the crystals and chemical 

 reactions, Biitschli 1 at first regarded them as crystals of oxalic acid, 

 but later 2 was content to regard them as the main end product of the 

 metabolism of proteids in the body. 



While numerous observers have experimented in various ways to 

 determine the chemical nature of these questionable bodies, the most 

 convincing results have been obtained by Schewiakoff ('94). After 

 repeated experiments, many of which only confirmed the earlier con- 



Fig. 148. Excretory granules in Paramcecium. [SCHEWIAKOFF.J 

 C. The isolated crystals. 



elusions of others, he obtained the following results: (i) the crys- 

 tals are insoluble, in the ordinary sense, in water ; (2) slightly soluble 

 in concentrated acetic acid and in dilute ammonia; (3) more soluble 

 in solutions of different salts, weak acetic acid, and ammonia ; 

 (4) easily soluble in mineral acids and alkalies ; (5) insoluble in alcohol, 

 ether, and carbon bisulphate ; (6) negative results with staining agents 

 showed that they can be neither albuminate nor carbohydrate in na- 

 ture ; (7) reactions to osmic acid, alcdhol, and ether excluded the 

 possibility of fats ; (8) delicate tests showed that the crystals were 

 composed of an unorganized substance ; (9) final tests showed this 



1 Protozoa, p. 103. 



*Loc. cit., p. 1484 



