CONNECTION BETWEEN BLOOD AND ITS GASES. 765 
by three, in order thai allowance may be made for the increased rate of 
flow in the blood of an active limb. 
As regards the velocity of the circulation, Finkler ] finds that the 
difference between the arterial and venous blood increases as the velocity 
diminishes. This relationship is well shown by Bernard's 2 observations 
upon the submaxillary gland. When the gland is at rest the venous blood 
is dark, but becomes almost arterial in colour when the gland becomes 
active and its blood vessels are dilated by stimulation of the chorda 
tympani. The difference between the arterial and venous blood is less 
marked, but the total absorption of oxygen and production of carbon 
dioxide are increased. 
In the last stage of asphyxia, the arterial blood contains only traces 
of oxygen. Thus Ludwig 3 gives, as the result of six analyses made by 
Setschenow and Holmgren upon asphyxiated dogs, 04 volume per cent, 
oxygen, 3 per cent, nitrogen, and 54 per cent, carbon dioxide ; and Zuntz 4 
has collected the results of nineteen analyses made by different observers, 5 
and obtains an average of - 9G volume per cent, oxygen, 2*07 per cent. 
nitrogen, 49"53 per cent, carbon dioxide. These values Zuntz contrasts 
with those obtained from averages of seventy -one analyses made by 
Prltiger and others upon normal arterial blood, namely, 18 - 3 volumes per 
cent, oxygen, 1-9 per cent, nitrogen, and 381 carbon dioxide; and he 
shows that the ratio between the increase of carbon dioxide and the loss 
of oxygen is 066 in asphyxia, as compared with 0'79 in the normal con- 
dition. This difference is to be explained by the retention of some carbon 
dioxide in the tissues, owing to the high tension of that gas in the blood. 
During apncea the arterial blood is almost saturated with oxygen, and 
contains about one-half its normal amount of carbon dioxide ; the venous 
blood, on the other hand, contains less oxygen as well as less carbon 
dioxide than it does in the normal condition. 6 These results confirm the 
work of Pfltiger, 7 who found that during apncea the respiratory exchange 
was not greater or smaller than in the ordinary condition of respiration. 
The changes which the blood undergoes in passing through the brain 
are much less marked than those which occur during its passage through 
muscles. Even during marked activity the brain has a comparatively 
small respiratory exchange. 8 
The nature of the connection between the blood and its gases.— 
Oxygen. — Magnus 9 in 1836 concluded that the gases of the blood were 
simply dissolved in that fluid, notwithstanding the fact that his experi- 
ments showed that the quantity of oxygen in the blood was much greater 
than the amount which could be dissolved in an equal volume of water 
exposed to air. Justus Liebig, 10 however, pointed out that Eegnault and 
Eeiset's n experiments showed that animals absorbed the same amount of 
oxygen whether they breathed pure oxygen or air ; he therefore urged 
1 Arch./, d. ges. Physiol., Bonn, 1875, Bd. x. S. 368. 
2 "Lecons sur les liquides de 1'organi.sme," Paris, 1S59, tome ii. p. 435 ; "Lecons sur la 
chaleur animate, " Paris, 1876, p. 185. 
3 Wien. med. Jahrb., 1865, Bd. xxi. S. 145. 
4 Hermann's "Handbuch," Bd. iv. Th. 2, S. 43. 5 See Zuntz, loc. tit. 
6 Ewald, Arch.f. d. ges. Physiol., Bonn, 1873, Bd. vii. S. 575. 
i Ibid., 1868, Bd. i. S. 100. 
8 Hill and Nabarro, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218. 
See also " Animal Heat," this Text-book, vol. i. p. 808. 
9 Ann. d. Phys. u. Chem., Leipzig, 1837, Bd. xl. S. 583 ; 1845, Bd. lxvi. S. 177. 
10 Ann. d. Chem. u. Pharm., 1851, Bd. Ixxix. S. 112. 
11 Ann. de chim. etphys., Paris, 1849, Ser. 3, tome xxvi. 
