Gases of the Blood 583 



To obtain a perfect seal in the whole of this apparatus, all the 

 connections of the different parts are submerged in water, strong 

 ligatures with rubber bands cut off the air completely, and besides, 

 a zinc cuff full of water forms a hydraulic seal at the union of the 



Fig. 24 — Mercury pump set up for the extraction of blood gases. A. Baro- 

 metric chamber. B. Movable bulb, communicating with A by 

 rubber and glass tube. C. Mercury reservoir for collecting the 

 gases. D. Balloon immersed in warm water, into which the blood 

 is conducted through cock r, after a vacuum has been made. The 

 large glass tube leading from D is surrounded by a current of 

 water which cools the gases and forms a hydraulic seal. R. Three- 

 way cock which can completely close the barometric chamber 

 (position 1), or connect A with G (position 2) or A with D 

 (position 3). 



