TJ1IY1RSITT 



THE BLOOD. 



alkali is not only combined with carbon dioxide but also with other 

 bodies, especially with albumin. The quantity of firmly chemically 

 combined carbon dioxide cannot be ascertained after pumping out 

 in vacuo without the addition of acid, because to all appearances 

 certain active constituents of the serum, as acids, expel carbon 

 dioxide from the simple carbonate. The quantity of carbon 

 dioxide not expelled from dog-serum by vacuum alone without the 

 addition of acid amounts to 4.9 to 9.3 vols. per cent, according to 

 the determinations of PFLUGER. 



From the occurrence of simple alkali carbonates in the blood- 

 serum it naturally follows that a part of the loosely-combined 

 carbon dioxide of the serum which can be pumped out must occur 

 as bicarbonate. The occurrence of this combination in the blood- 

 serum has been directly shown. In experiments with the pump, 

 as well as in absorption experiments, the serum behaves in other 

 ways as a solution of bicarbonate, or carbonate of a corresponding 

 concentration; and the behavior of the loosely-combined carbon 

 dioxide in the serum can be explained only by the occurrence of 

 bicarbonate in the serum. By means of vacuum the serum always 

 allows much more than one half of the carbon dioxide to be expelled, 

 and it follows from this that in the pumping out not only may a 

 dissociation of the bicarbonate take place, but also a conversion of 

 the double sodium carbonate into a simple salt. As we know of no 

 other carbon-dioxide combination besides the bicarbonate in the 

 serum from which the carbon dioxide can be set free by simple dis- 

 sociation in vacuo, we are obliged to assume that the serum must 

 contain other faint acids in addition to the carbon dioxide, which 

 contend with it for the alkalies and which expel the carbon dioxide 

 from simple carbonates in vacuo. The carbon dioxide which is 

 expelled by means of the pump and which, without regard to the 

 simple absorbed quantity, is generally designated as " loosely chemi- 

 cally combined carbon dioxide," is thus only obtained in part in 

 dissociable loose combination; in part it originates from the sim- 

 ple carbonates, from which it is expelled in vacuo by other faint 

 acids. 



These faint acids are thought to be in part phosphoric acid and 

 in part globulin. The importance of the alkali phosphates for the 

 carbon dioxide combination (see page 97) has been shown by the 



