414 L. H. HYMAN. 



SUMMARY AND CONCLUSIONS. 



1. The normal oxygen consumption and the oxygen con- 

 sumption in the presence of various concentrations of potassium 

 cyanide was tested in the case of Pennaria, Metridium, Nereis, 

 Chcetopterus, Arenicola, two species of leeches, and two species 

 of aquatic oligochaetes. In all cases, numbering about seventy 

 experiments (not all of which are reported), the oxygen con- 

 sumption was markedly decreased in the presence of cyanide. 



2. This decrease was not due to differences in muscular activity, 

 since in some of the experiments it was possible to keep the 

 animals entirely quiet throughout, while in the others, with 

 three exceptions noted in the text, the animals were equally 

 active in both the normal and the cyanide-containing water. 

 None of the concentrations of cyanide used caused any visible 

 anaesthesia, within the short time periods during which the 

 animals were exposed to them. 



3. The decrease was reversible, the oxygen consumption 

 returning to approximately the original value when the cyanide 

 was washed out of the animals. In no case were the animals 

 injured in any way. Most of them were kept for a considerable 

 length of time after the experiments were completed and were 

 entirely normal in behavior and appearance. 



4. As was found to be the case in previous experiments with 

 cyanide, the percentage of decrease is absolutely greater, the 

 more concentrated the cyanide solution, but the more dilute 

 solutions are relatively more effective. 



5. These results are in accord with previous experiments on 

 the action of cyanides and justify the use of the cyanides as 

 depressing agents. 



LITERATURE. 

 Allen, G. D. 



'19 Quantitative Studies on the Rate of Respiratory Metabolism in Planaria. 

 I. The Effect of Potassium Cyanide on the Rate of Oxygen Consumption. 

 Amer. Jour. Physiol., Vol. 48, pp. 93-121. 

 Child, C. M. 



"19 A Comparative Study of Carbon Dioxide Production during Starvation in 



Planaria. Amer. Jour. Physiol., Vol. 48, pp. 231257. 

 Child, C. M., and Hyman, L. H. 



'19 The Axial Gradients in Hydrozoa. I. Hydra. BIOL. BULL., Vol. 36, pp. 

 183-223. 



