Gases of the Blood 



599 



apparatus the framework which holds the dog. The operator enters 

 the cylinder at the same time, and passes through one of the holes, 

 with which the wall is riddled at that point like the head of a 

 watering-pot, the serre-fine D, whose long handle d remains out- 



Fig. 30 — Extraction of blood from an animal under decreased pressure: A 

 artery; P wall of the apparatus; S serre-fine; a cannula placed in 

 the artery; s syringe extracting the blood (its lower armature 

 must be entirely immersed in water). 



side. Then spreading apart the two jaws of the serre-fine, so as to 

 make the little guide-rods leave their holes, he brings the carotid 

 in to the space d," from which it cannot slip, thanks to the bolts; 

 the movable lever d, controlled from the outside by the handle d, 

 permits him to compress the artery as low as possible. He then 

 opens the artery, and inserts in it the metal cannula, the end of 



