1920 Fli/rnanj on Oxiif/en Consumption 391 



In this dilution, anaesthesia did not occur ; nevertheless the oxygen con- 

 sumption again fell during the exposure to cyanide. 



Particular note was also made of the condition of respiratory pro- 

 cesses and structures during the experiments. No differences were ob- 

 served in the degree of extension of the tube feet and branchiae of the star- 

 fish and sea-urchins, the tentacles of the holothurians, or the gills of the 

 nudibranchs in normal and cyanide-containing sea-water. In the case of 

 Mytilus, it seemed to me that the siphons were not so widely open during 

 the exposure to' cyanide as before. This may account for part of the very 

 great decrease of oxygen consum})tion observed in the case of these 

 animals. 



In general, then, it may be said, both from these and from previous 

 experiments, that the decrease in the rate of oxygen consumption which 

 occurs in the presence of potassium cyanide is not due to any effect of the 

 cyanide upon either muscular activity or respiratory mechanisms but must 

 be ascribed to some direct action of the cyanide upon the respiring proto- 

 plasm. The nature of this action has not yet been ascertained with certainty 

 but the opinion of the majority of investigators favors the idea that it is 

 chemical, i. e., that the cyanide unites with the protoplasm. 



That the action of the cyanide is reversible has already been shown 

 in previous experiments (Hyman, 1916, 1919a, 1919b). After the ani- 

 mals are returned to normal water, the oxygen consumption returns to the 

 normal value, provided that otlier factors have been eliminated, ^^'hen, 

 however, animals are removed from their environments and kept in captiv- 

 ity for experimental purposes, their rate of oxygen consumption falls rather 

 rapidly at first. This fall is probably due to starvation. The materials 

 used in the ])resent experiments were all freshly collected animals and it 

 was therefore impractical to determine whether or not the oxygen con- 

 sumption returned to the normal value after exposure to cyanide since 

 the oxygen consumption would fall anyway owing to starvation or other 

 factors. These factors would not affect the oxygen consumption within 

 the four or five hours r('(]ulrt(l for each experiment hut would be in evi- 

 dence by the following day. Owing to these circumstances, the oxygen 

 consumption on the day following exposure to cyanide may or may not be 

 as high as before such exposure. In some tests made in connection with 

 the present experiments results of this nature were obtained. In some of 

 the individuals tlie oxygen consumjjtion had returned to the original figure 

 on the following clay, while in others it was lower than originally. As 

 already stated this latter result commonly occurs whether the animals have 

 been exposed to the cyanide or not. Not much attention was paid to the 

 question of the reversability of the action of cyanide in the jiresent experi- 

 ments as the reversibilitv has alreadv been sufficient! v {Icmonstratcd in 



