572 ASA A. SCHAEFFER 



small pseudopods thrown out on the side where the uric acid 

 lay— 1125. 



In the path of a large clear raptorial binucleate ameba was then 

 placed a grain of uric acid — 1142. There was first a tendency to 

 move away but presently positive reactions set in and the ameba 

 flowed into contact with the acid and then surrounded it. The 

 acid was partly enclosed in the protoplasm. The whole behavior 

 seemed like a modified feeding reaction. But the uric acid had 

 apparently not been completely surrounded by the protoplasm, 

 for about six minutes later it was left behind. A grain of globu- 

 lin was then treated in a similar manner. Although a food cup 

 was formed over it, the globulin was not ingested. This ameba 

 responded very readily to 'tickling.' 



These experiments show that the stimulating power of uric 

 acid is feebler than that of globulin or carmine, but it seems to be 

 strong enough, nevertheless, to produce ingestion under certain 

 conditions. As in all cases where dissociation is incomplete it 

 is difficult to decide whether the stimulating element is the un- 

 dissociated molecule, the ions, or both together. It is certain, 

 however, that the acid in solution possesses the power of stimu- 

 lation, for such behavior as is observed in figures 1120, 1121, 

 1143 could hardly be explained if the uric acid in solution was 

 without effect. 



Uric acid does not seem to be regarded as possessing food prop- 

 erties after it is eaten. This is shown by the short interval of 

 time, only a few minutes, that elapses between eating and excre- 

 tion. Uric acid does not act as an injurious substance when once 

 inside the body, for in one case a grain of uric acid which was in- 

 gested with a grain of globulin remained at least thirty-five 

 minutes in the ameba's body. Whether uric acid can be broken 

 up to any extent by digestive action is not known, and it is con- 

 sequently impossible to say whether uric acid possesses food value 

 or not. 



Solid egg white. The white of several hen's eggs that had been 

 in an incubator for forty-eight hours was poured into an open 

 glass dish and then placed in an incubator where the tempera- 

 ture ranged from 30° to 38°C. In the course of a day or two the 



