THE BLOOD. 103 



the amount of carbon dioxide of the gas mixture corresponds as 

 nearly as possible in the beginning to the probable tension of this 

 gas in the blood, we may learn the tension of the carbon dioxide in 

 the blood. 



According to this method, the carbon-dioxide tension of the 

 arterial blood is on an average 2.8$ of an atmosphere, correspond- 

 ing to a pressure of 21 mm. mercury (STRASSBURG). In the blood 

 from the pulmonary alveoli NUSSBAUM found a carbon-dioxide ten- 

 sion of 3.81$ of an atmosphere, corresponding to a pressure of 28.95 

 mm. mercury. STRASSBUKG, who experimented on tracheotomized 

 dogs, in which the ventilation of the lungs was less active and 

 therefore the carbon dioxide was removed from the blood with less 

 readiness, found in the venous blood of the heart a carbon-dioxide 

 tension of 5.4$ of an atmosphere, corresponding to a partial pressure 

 of 41.01 mm. mercury. 



Another method is the catheterization of a flap of the lungs. 

 By the introduction of a catheter of a special construction into a 

 branch of a bronchia the corresponding flap of the lung may be 

 hermetically sealed, while in the other flaps of the same lung and 

 in the other lung the ventilation remains unhindered, so that no 

 stowing of carbon dioxide takes place in the blood. When the 

 cutting off lasts so long that a complete equalization between the 

 gases of the blood and the cut-off air of the lungs is assumed, a 

 sample of this air of the lungs is removed by means of the catheter 

 and analyzed. In the air thus obtained from the lungs NUSSBAUM 

 and WOLFBERG found an average of 3.6$ C0 2 . NUSSBAUM has 

 also determined the carbon-dioxide tension in the blood of the 

 pulmonary alveoli in a case simultaneous with the catheterization 

 of the lungs. He found nearly identical results, namely, a carbon- 

 dioxide tension of 3.84$ and 3.81$ of an atmosphere. 



While according to the just-mentioned determinations the car- 

 bon-dioxide pressure in the venous blood amounts to about 30 mm. 

 mercury and in the arterial to about 20 mm., BOHR has, on the con- 

 trary, according to the above-described methods (page 101), found 

 strikingly lower figures 2 to 3 mm., and even lower than 1 mm. 



The quantity of carbon dioxide in the expired air amounts to 

 about 2.8$ (WOLFBERG, BOHR). The air of the alveolus of the 

 lungs is naturally richer in carbon dioxide, but the amount is not 



