77° 
CHE MIS TR Y OF RESPIRA TION. 
Further proofs that the nitrogen is simply in solution are afforded by 
two experiments made by Prliiger. Blood subjected to the vacuum of a 
mercurial pump quickly gives off its nitrogen; thus at 0° 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 T626, and that for sheep's blood 
with a specific gravity of 1052 was 1*547 at C . 
Partial Pressure of CO2 in the 
Mixture of Gases Used. 
Carbon Dioxide in Dog's Serum (0° and 760 Mm.). 
Mm. mercury. 
Percentage 
of an 
Atmosphere. 
Total. 
Ouantitv Absorbed Q" an tit.V in Chemical 
yuantit.\ Absorbed. . Combination. 
105-8 
351-4 
747-S 
13-9 
46-2 
98-4 
61'1 per cent. 
122-1 
202-2 
20-7 per cent. 
68-8 
146-4 
46-4 per cent. 
53-3 
55-8 
1 Piliiger, " Die Kohlensaure des Blutes," Bonn, 1864, S. 12. 
" Pfliiger, Arch.f. d. gcs. 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, Mim. Acad. imp. d. sc. de St. Pdtersbourg, 1879, tome xxvi. p. 6; Zuntz, " Beitr. 
z. Physiologie des Blutes," Inaug. Diss., Bonn, 1868, S. 33. 
4 Buchanan, Proc.Roy. Soc. London, 1874, No. 15, p. 192. 
: '"P>eitr. z. Physiol, des Blutes/' S. 39; Hermann's "Handbuch," Bd. iv. Th. 2, 
S. 15. 
