670 



PHYSIOLOGY OF RESPIRATION. 



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 

 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 



Fig. 272. Gas pump for extracting the gases of blood (Grehanf): M and F, Mercury 

 receivers; P, windlass for raising and lowering M ; m, a three-way stop-cock 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 intro- 

 duced by the graduated syringe, S. By means of the stop-cock m the vacuum in F , caused by 

 the fall of the mercury, can be placed in communication 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. 



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 stop-cock are driven into 

 a burette fastened over the opening of the tube in C. To drive off all of the 

 carbon dioxid a little dilute phosphoric acid must be added to the blood in 

 B by means of the syringe, S. The gases thus collected into the burette are 

 first measured and are then analyzed for the three important constituents 

 by some of the accepted gasometric methods. The principle involved is to 



