Action of Carbonic Acid 899 



and 17, that it is from 24 to 28 for sparrows, and that it reaches 

 and passes 30 for mammals. 



2. The Lethal Concentration of Carbonic Acid in the Blood. 



In the experiments the report of which follows, I tried first to 

 determine the lethal concentration of carbonic acid, not in the 

 exterior medium, but in the blood; next, to ascertain the relations 

 which exist between the increasing amount of this gas in the air 

 in which the animal is confined, and the quantity in the blood. 



Evidently these experiments could be made only on dogs and I 

 could not try in practice to keep them in closed vessels in com- 

 pressed air. I therefore had to use the method of respiration in 

 superoxygenated air at normal pressure. 



The set-up of the apparatus was very simple. The animal, which 

 was securely fastened, was forced to breathe either through a 

 tightly closed muzzle or directly through the trachea into a very 

 large rubber bag slightly inflated with oxygen. A small opening 

 permitted us to draw air samples at various intervals, taking great 

 precautions that the sample might represent the average composi- 

 tion of the air in the bag. 



Let us now consider the report of these experiments: 



Experiment DCV. February 14. Dog weighing 6.5 kilos: sick, its 



pneumogastric having been cut 4 days before. 



3 o'clock. Placed a tube in the trachea. Caused to breathe into 



the rubber bag in which air is introduced. After 10 minutes, I draw 



70 cc. of blood from the femoral artery .... A 

 Removed to free air. 



3:35. Caused to breathe into the bag, which then contains a mix- 

 ture with 94% of oxygen. After 15 minutes, drew 70 cc. of blood . . . B 

 5:15. The animal draws deep breaths. Drew 44 cc. of blood . . . . C 

 9 o'clock. The eye is hardly sensitive; 15 to 16 respirations, in 



groups of three, like those of tortoises; rectal temperature 27°. 



The gas of the bag contains CO. 28; 2 60; C0 2 + O* = 88; there 



has very evidently been absorbed a quantity of oxygen corresponding 



to 6%. 



I draw 37 cc. of blood, which comes with difficulty . . . . D 



I let the animal breathe in the open air. 



A (air) contains per 100 cc. of blood O, 16; CO, 29.5 



B (oxygen) contains per 100 cc. of blood O, 18.4; CO, 20.6 



C contains per 100 cc. of blood O, 17.5; CO. 50.1 



D (CO,: 28; O,: 60.) contains per 100 cc. of blood O, 17.9; CO, 68.4 



At 10 o'clock, the animal is still breathing in the same way, and 



at the same temperature. 



Found dead the next day. 



Experiment DCV I. February 16. Very sturdy dog, weighing 15 

 kilos. 



