CARBON DIOXIDE IN THE BLOOD. 853 



alkali diphosphate takes place. It is generally admitted that the blood- 

 coloring matters, especially the oxyhaemoglobin, which can expel carbon 

 dioxide from sodium carbonate in vacuo, acts like an acid, and as the 

 globulins also act similarly (see below), these bodies may also occur in 

 the blood-corpuscles as an alkali combination. The alkali of the blood- 

 corpuscles must, therefore, according to the law of mass action, be divided 

 between the carbon dioxide, phosphoric acid, and the other constituents 

 of the blood-corpuscles which possess acidic properties, and among these 

 especially the blood pigments, because the globulin can hardly be of 

 importance on account of its small quantity. By greater mass action 

 or greater partial pressure of the carbon dioxide, bicarbonate must be 

 formed at the expense of the diphosphates and the other alkali combina- 

 tions, while at a diminished partial pressure of the same gas, with the 

 escape of carbon dioxide, the alkali diphosphate and the other alkali 

 combinations must be reformed at the cost of the bicarbonate. 



Haemoglobin must nevertheless, as the investigations of SETSCHENOW l 

 and ZUNTZ, and especially those of BOHR and ToRUP, 2 have shown, be 

 able to hold the carbon dioxide loosely combined even in the absence 

 of alkali. BOHR has also found that the dissociation curve of the car- 

 bon dioxide haemoglobin corresponds essentially to the curve of the 

 absorption of carbon dioxide, on which ground he and TORUP consider 

 the haemoglobin itself as of importance in the binding of the carbon 

 dioxide of the blood, and not its alkali combinations. According to 

 BOHR the haemoglobin takes up the two gases, oxygen and carbon dioxide, 

 simultaneously by the oxygen uniting with the pigment nucleus and the 

 carbon dioxide with the protein component. But as according to the 

 researches of ZUNTZ 3 the combination of haemoglobin with the alkali is 

 first split to any great extent with a carbon dioxide tension of more than 

 70 mm., it must be admitted that with the ordinary CO2 pressure in 

 the organism, the combination of the carbon dioxide in the blood cor- 

 puscles does not essentially take place through the agency of the alkali 

 but chiefly by means of the haemoglobin. 



The chief part of the carbon dioxide of the blood is found in the 

 blood-plasma or the blood-serum, which follows from the fact that the 

 serum is richer in carbon dioxide than the corresponding blood itself. 

 By experiments with the air-pump on blood-serum it has been found 

 that the chief part of the carbon dioxide contained in the serum is given 

 off in a vacuum, while a smaller part can be removed only after the 



1 Centralbl. f. d. med. Wissench., 1877. See also Zuntz in Hermann's Handbuch, 

 76. 



2 Zuntz, 1. c., 76; Bohr, Maly's Jahresber., 17; Torup, ibid. 



3 Centralbl. f. d. med. Wissensch., 1867. 



