770 



CHEMISTR Y OF RESPIRA TION. 



Further proofs that the nitrogen is simply in solution are afforded by 

 two experiments made by Pniiger. Blood subjected to the vacuum of a 

 mercurial pump quickly gives off its nitrogen ; thus at all the nitrogen, 

 but less than half the oxygen and three-quarters of the carbon dioxide, 

 were given off in twenty hours. 1 The blood of a dog which had pre- 

 viously breathed for a few minutes a mixture containing only oxygen 

 and carbon dioxide, yielded no nitrogen to a vacuum ; that gas had 

 rapidly diffused from the blood into the air of the lungs. 2 



Carbon dioxide. The nature of the connection between the carbon 

 dioxide and the blood, which contains it, is very difficult to follow, and 

 has given rise to much discussion. 3 There is no single substance with 

 which the whole of the carbon dioxide is combined ; it is present both 

 in the red corpuscles and plasma, and, after coagulation of the blood, 

 in both the clot and serum. It will be well, therefore, to consider 

 (1) The amount of this gas, which may be in a state of simple solution 

 in the blood and in serum ; (2) the quantity in loose and firm chemical 

 combination with substances in the corpuscles and in the plasma and 

 serum of the blood. 



Carbon dioxide is much more soluble in water than oxygen and 

 nitrogen. Plasma and serum are not able to retain in simple solution 

 as much carbon dioxide as can a similar volume of pure water, for it 

 has already been mentioned that the presence of indifferent substances 

 in solution diminishes the capacity of the fluid to absorb gases. There 

 are, however, exceptions 4 to this general rule, and it is therefore 

 necessary to determine experimentally the absorption coefficient of 

 carbon dioxide in blood before we conclude that it is less than in water. 

 This experiment was made by Zuntz, 5 who neutralised the blood with 

 phosphoric or oxalic acid in order to eliminate its chemical affinity, 

 saturated it with carbon dioxide, and then determined the amount 

 absorbed. He found that the coefficient of absorption for calves' blood 

 with a specific gravity of 1038 was 1*626, and that for sheep's blood 

 with a specific gravity of 1052 was T547 at 0. 



1 Pfliiger, " Die Kohlensaure des Blutes," Bonn, 1864, S. 12. 

 2 Pfluger, Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 104. 



3 For further details see Zuntz, Hermann's "Handbuch," Bd. iv. Th. 2, S. 64; 

 Hammarsten, " Lehrbueh der physiologischen Chemie," Wiesbaden, 1895, S. 535; Setsche- 

 now, Mem. Acad. imp. d. sc. de St. Pttersbourg, 1879, tome xxvi. p. 6; Zuntz, " Beitr. 

 z. Physiologic des Blutes," Inaug. Diss., Bonn, 1868, S. 33. 



4 Buchanan, Proc. Roy. Soc. London, 1874, No. 15, p. 192. 



5 "Beitr. z. Physiol. des Blutes," S. 39; Hermann's "Handbuch/' Bd. iv. Th. 2, 

 S. 15. 



