Carbon Assimilation and Respiration 13 



Peptone 0.2 per cent. 50 



Peptone 0.4 per cent. 4.2 



Peptone 1.0 per cent. 0 



Peptone 2.0 per cent. 0 



Dextrose 0.25 per cent. 333 



Dextrose 1.00 per cent. a 120 



Tvrosin 0.1 per cent. C4 



Glycocoll 0.1 per cent. 100 



Glvcocoll 0.5 per cent. 45 



Urea 0.1 per cent. 100 



Urea 0.5 per cent. 57 



Ethvl Alcohol 0.1 per cent. 54 



Ethyl Alcohol 0.3 per cent. 46 



Amyl Alcohol 0.1 per cent. 43 



Amyl Alcohol 0.3 per cent. 28 



Normal atmospheric pressure 100 



C0 2 -free atmosphere 60 



Increased C0 2 pressure 300 



Hydrogen atmosphere 50 



Increased atmospheric pressure (5-10 per cent.) 130 



Beduced atmospheric pressure (10 per cent.) 100 



It is seen from the above data that the nitrates have a depress- 

 ing effect upon the respiration of the organism while the sulfate 

 does not. 0.025 molar concentration of the nitrate is sufficient 

 to reduce respiration to 27-29 per cent. ; 0.05 molar only to about 

 10-20 per cent., while still higher concentrations practically de- 

 press respiration. The action of nitrates is not antagonized by 

 the presence of ammonium sulfate, since 0.025 molar nitrate 

 depresses respiration in the presence of an equimolar concentra- 

 tion of ammonium sulfate to the same extent as in its absence. 



Peptone proves to be another substance injuring respiration 

 even in comparatively small concentrations. The injurious action 

 of nitrates and peptone can also be readily demonstrated by 

 adding these substances to the culture media upon which the 

 organism is grown. The amino acids and acid amides have some 

 depressing effect, but not to such an extent as peptone. 



Cyanides repress respiration completely, even in concentra- 

 tions of 0.0004 molar. Dextrose has no depressing effect on 

 respiration, even a 1 per cent, concentration tends to favor it. 



The influence of the gas pressure is of particular interest, 

 particularly that of carbon dioxide. When the flasks, in which 

 respiration was taking place, were covered with air tight bell 

 jars, it was found that a C0 2 -free atmosphere reduces respira- 

 tion to 60 per cent., while an atmosphere rich in C0 2 (which 

 was allowed to bubble from a gas tank into the bell jar) in- 



