CHANGES IN AIR AND BLOOD IN RESPIRATION. 



597 



all joints being protected from leakage by a seal of water outside, as shown 

 at h, which represents a piece of wide rubber tubing filled with water so as 

 to protect a joint between two pieces of glass tubing. B is next exhausted 

 completely by raising and lowering M a number of times in the way described 

 above until on throwing B into communication with a vacuum in F no further 

 gas is given off. The last particles of air may be driven out from B by boil- 

 ing a little water in it. After a complete vacuum has been established in B 



Fig. 244. Gas pump for extracting the gases of blood (Grehant) : M and F f 

 The mercury receivers; P, the windlass for raising and lowering M; m, a three-way 

 stopcock protected by a seal of mercury or water; C, a cup with mercury over which 

 the receiving eudiometer is placed to collect the gases; B, the bulb in which, after a 

 vacuum is made, the blood is introduced by the graduated syringe, S. By means of the 

 stopcock m the vacuum in F, caused by the fall of the mercury, can be placed in communi- 

 cation with B. After the gases have diffused over into F, M is raised, and when the stop- 

 cock m is properly turned these gases are driven out through C into the receiving tube. 

 The operation is repeated until no more gas is given off from B. 



a measured amount of blood is introduced from a graduated syringe, S, as 

 represented in the figure. This blood must be taken directly from the vessels 

 of the animal and be introduced into B at once. B is kept immersed in water 

 at the temperature of the body, and the bulb M is now raised and lowered a 

 number of times so that the gases given off from the blood are drawn over 

 into F and then by proper manipulation of the stopcock are driven into 



