2l8 E. J. LUND. 



eight hours irritability was practically lost in those living in 

 hydrogen. The animals in air were normal. The loss of irri- 

 tability is clearly correlated to the fall in rate of CO 2 elimination 

 during the last seven-hour period. All animals in this twenty- 

 eight-hour period in hydrogen recovered when removed to air. 



Another similar experiment which lasted thirty-eight hours 

 gave similar results. A fall in rate of CO 2 elimination in hydrogen 

 was again associated with loss of irritability and muscular tone. 

 One set of animals in the thirty-eight-hour period only partially 

 recovered when removed to air-saturated water. The controls 

 in air were normal. 



It is evident that the loss of irritability and appearance of a 

 condition which closely resembles narcosis is correlated more 

 closely to decrease in rate of CO 2 production than the lack of 

 free oxygen. 



An important fact to notice is that the action of KNC and 

 the effect of absence of free oxygen are quite distinct. The 

 experiments above show clearly that the rate of CO 2 elimination 

 is not noticeably changed for hours after free oxygen has been 

 removed. Potassium cyanide in proper concentrations inhibits 

 oxygen consumption to as much as 70 to 80 per cent., as shown 

 by Allen ('19, I.) and confirmed by Hyman ('19), and also mark- 

 edly inhibits carbon dioxide elimination as found by Child ('19). 

 While the absence of free oxygen does not affect the rate of CO 2 

 production for many hours, so far as the evidence goes, the return 

 of Planaria to air-saturated water from KNC solutions strong 

 enough to cause an inhibition of 50 to 80 per cent, does not 

 result in an increase in the rate of oxygen consumption, after 

 the return to air-saturated water, as is the case after life in the 

 absence of free oxygen. Another fact to be noted is that it has 

 not so far been possible to obtain a complete inhibition of the 

 oxygen consumption in Planaria agilis by means of KNC. These 

 differences in the action of KNC and lack of oxygen have not 

 been fully recognized by previous investigators, while it has 

 often been assumed that lack of oxygen and KNC solutions 

 have the same effects. 



