Gases of the Blood 



645 



ditions, the oxygen which would have been present in excess be- 

 cause of the reduced pressure could escape from the blood, which 

 was supersaturated at this new pressure. The flask was large 

 enough in proportion to the quantity of blood, so that the oxygen 

 thus set free was absolutely negligible. Furthermore, I made sure 

 by a simple procedure that the pressure had not varied perceptibly 

 during the agitation. 



Fig. 42 — Water motor shaking the flask containing the blood to be satu- 

 rated with oxygen. 



When this was done, I took a new sample of the blood for 

 analysis of the gases. 



Since I placed in the flask about 200 cc. of blood, it was possible 

 for me to make several analyses with the same blood at different 

 pressures. 



Later, a useful improvement was added to this method, whose 

 principal cause of error lies in the difficulty of shaking hard enough 

 with the hand. The flask was firmly fixed on a plank which was 

 vigorously moved by a little water motor (Fig. 42). Under these 

 conditions, the saturation of the blood was accomplished with great 

 rapidity, and a few whirls of the sling were enough to dispel the 

 froth and the bubbles of gas in suspension. 



