OXYGEN. 



421 



this gas is merely dissolved both by the plasma and by the red corpuscles, 

 following the laws of gas absorption. The average gas pressure of the 

 carbon dioxide in the organism may be taken as 30 millimeters. Cor- 

 responding to this pressure, the amount of carbon dioxide physically 

 dissolved in 100 cubic centimeters of blood amounts to 2.01 cubic centi- 

 meters. Now the total amount of carbon dioxide absorbed under these 

 conditions is about 40 per cent by volume, so that approximately only 

 5 per cent of the total carbon dioxide absorbed is merely held in solution. 



It is of interest to know how the carbon dioxide is distributed between 

 the blood-corpuscles and the plasma. According to Setschenow, 1 about 

 two-thirds of the carbon dioxide in dog's blood is held by the plasma, and 

 one-third by the blood corpuscles. Kraus 2 found similar values with the 

 blood of oxen. In blood from horses, however, Fre*de*ricq 3 found only 

 one-fourth with the corpuscles and three-fourths with the plasma. 



A. Jaquet 4 studied the influence of the carbon dioxide gas pressure upon 

 the absorption of the gas by the plasma at 37.5 C. The absolute values 

 of this absorption vary greatly. They depend upon the alkalinity of the 

 plasma. Although the values given in the following table are, therefore, 

 only relatively true, still they show how the amount absorbed depends 

 upon the pressure exerted by the gas. 



CARBON DIOXIDE ABSORPTION BY THE SERUM. 



It is evident from the above figures that with low pressures there is a 

 marked increase in the absorption with increasing pressure. With pres- 

 sures above 20 millimeters, however, this increase is not so marked. 



Let us now see what the nature of the chemical combination is between 

 the carbon dioxide and the plasma. First to be considered are the salts 

 of the alkalies, especially carbonates. The amount of these present in the 

 plasma is quite large, the sodium salts predominating. Now we know that 

 monocarbonates are changed to bicarbonates by the absorption of carbon 

 dioxide, and conversely that loss of the same gas gives rise to the form- 

 ation of monocarbonates again. It would thus be very easy to account 

 for the transportation of the carbon dioxide by the blood. In reality, 



1 Memoires de 1'Acad. de St. Petersburg, 26, 59 (1879). 

 3 Festschrift Graz. p. 19 (1898). 



3 Compt. rend. 84, 661 (1877); 85, 48 (1878). 



4 Arch, exper. Path. Pharm. 30, 311 (1892). 



