156 The Controlling Influence of Carbon Dioxide. 



6. AVhere oxygen is in deficiency so that some degree of anaerobic CO2 

 production occurs, it is then found that carbon dioxide has no retarding 

 effect on oxidation. 



„ 7. A quantitative relation exists between the concentration of carbon 

 dioxide and the depression of aerobic respiration of the same order as in the 

 case of anaerobic CO2 production. 



8. These results are taken as evidence that anaerobic and aerobic CO* 

 production are processes genetically connected in normal respiration, and 

 that the rate of the anaerobic process acts as the limiting factor in normal 

 respiration. 



9. Of the two types of respiration demonstrated by Blackman and others, 

 namely, floating respiration and protoplasmic respiration, it is the former 

 only which is depressed by the retarding action of carbon dioxide. 



10. The main conclusion to be drawn from these results with regard to the 

 inhibitory action of C0 2 upon growth is that a marked reduction of respira- 

 tion is involved in the mechanism of CO2 narcosis. 



In conclusion I wish to thank Dr. F. F. Blackman, who has continually 

 given me most valuable help in consultation during these researches, and 

 also Prof. V. H. Blackman, for whose criticism and advice I am much 

 indebted. 



