THE RESPIRATION APPARATUS. 35 



late, and measuring the residual nitrogen. The form of apparatus is 

 shown in figure 16. 



The apparatus consists essentially of two burettes, water- jacketed to 

 secure more constant temperature, and connected by a 3-way cock, 

 which in turn is joined to the regular Hempel gas-pipette. The 3-way 

 cock and glass connections are made of capillary glass tubing. 



Each fresh cylinder of oxygen is connected by a metal yoke from its 

 valve with a T tube, one arm of which dips under a little water and the 

 other arm of which is connected with a soda-lime U tube and thence with 

 the capillary tube T leading to the burettes. Before connecting with 

 this capillary tube, however, the oxygen is allowed to flow for several 

 minutes through the soda-lime tube with just enough pressure not to 

 bubble through the water of the escape. The burette B 2 and capillary 

 tube T have been previously filled with water by opening the 3-way 

 cock C and raising the reservoir R 2 , thus expelling the air from the 

 apparatus into the room and leaving the burette B 2 and the tube T 

 filled with water. The stopcock C is then closed and the reservoir R 2 

 lowered and hung at such a level that the water in the burette will drop 

 to about the 100 cc. mark when the stopcock C is opened. The soda- 

 lime U tube is connected with the capillary tube T, the oxygen mean- 

 while bubbling through the escape, the stopcock C slowly opened, and 

 oxygen drawn into the burette, the bubbling ceasing or nearly ceasing 

 while the burette fills. When the level of the water in B 2 is the same 

 as that in Rj the stopcock C is closed and the current of gas through 

 the soda-lime tube stopped by closing the valve on the cylinder. After 

 allowing the water to drain down the side of the burette B 2 for a definite 

 length of time (five minutes), the reservoir R 2 is held immediately 

 behind the burette B 2 in such a manner that the level of water in both 

 is the same. The readings of the volume of gas in the burette B 2 are 

 then recorded. By means of gentle suction with the mouth the capil- 

 lary tube and a portion of the rubber tube R which is attached to a 

 Hempel pipette containing a solution of potassium pyrogallate are filled 

 with the pyrogallate solution and the rubber tube tightly closed by means 

 of a pinchcock P. The section of the rubber tube above the pinch- 

 cock is then completely filled with water and attached to the capillary 

 tube T. The connection with the cylinder first being broken, the 

 pinchcock is then opened, slipped on the glass capillary tube T, the 

 stopcock C turned in such a manner as to connect the burette B. 2 directly 

 with the Hempel pipette, and by raising the reservoir R 2 the oxygen is 

 transferred to the pipette. The last traces of gas can be removed from 

 the burette and both capillary tubes by forcing through them water 



