132 A CHEMICAL SIGN OF LIFE 



the nitrometer C. Increase the pressure inside of the 

 nitrometer C by raising the safety bottle D above the 

 level of the alkali in the nitrometer, and then open 

 stopcock /. In this ' way the excess of mercury left 

 in the capillary tube will be pushed over into the 

 chamber A and flow through stopcock 4 into a receiv- 

 ing vessel. 



If stopcocks 2 and 3 are absolutely air-tight, there 

 should be no air bubble present in the tube B on standing. 

 This being assured, a known amount of mercury is intro- 

 duced into the chamber A by means of mercury burette 

 H } thus making the capacity of the chamber what was 

 desired. Tissue is introduced into the chamber in the 

 usual manner, the glass stopper is replaced, the chamber 

 is sealed with mercury, and the nitrometer is filled with 

 air free from carbon dioxide. After evacuation of the 

 chamber and introducing pure air several times, stop- 

 cock 5 is closed and the time is recorded, the pressure is 

 adjusted, and stopcock 2 is turned 45. At the end of 

 the desired period of respiration any portion of the air, 

 say 10 or 15 c.c., from the chamber can be driven into 

 tube B. This is accomplished by raising the right-hand 

 mercury burette H and by simultaneously opening 

 stopcocks 2 and 4 and gradually lowering the left-hand 

 mercury burette G. Stopcock 2 is now closed and the 

 pressure of the air in B is made equal to that of the 

 atmosphere and is kept under this condition, having 

 the mercury burette G at the proper height. 



Remove mercury from the stopper 5 and unstop the 

 chamber, take away the tissue, and lower the mercury 

 burette H so that all the mercury in the chamber will 

 flow back into the burette. The little excess of mercury 



