GASES OF THE BLOOD. 851 



experiments, calculated for C. and 760 mm. mercury pressure. The 

 nitrogen seems to be simply absorbed by the blood, at least in great 

 part. It appears, like argon, to play no direct part in the processes of 

 life, and its quantity varies but slightly in the blood of different blood- 

 vessels. 



The oxygen and carbon dioxide behave otherwise, as their quantities 

 have significant variations, not only in the blood from different blood- 

 vessels, but also because many factors, such as a difference in the rapidity 

 of circulation and the ventilation of the lungs, a different temperature, 

 alkalinity of the blood, rest and activity cause a change. In regard to the 

 gases they contain, the greatest difference is observable between the blood 

 of the arteries and that of the veins. 



The quantity of oxygen in the arterial blood (of dogs) is on an average 

 22 vols. per cent (PFLUGER, BOHR and HENRIQUES). In human blood 

 SETSCHENOW found about the same quantity, namely, 21.6 vols. per 

 cent. LEOWY in another manner has determined the quantity of oxygen 

 which the blood can take up by first shaking human venous blood with 

 air and then calculating from this the quantity of oxygen in human 

 arterial blood. He calculates the average amount as 18 vols. per cent. 

 Lower figures have been found for the blood of herbivora (such as horse, 

 sheep, rabbits) and birds (hen and ducks) namely, 14-10.7 per cent (ZUNTZ 

 and HAGEMANN, SCZELKOW, WALTER, JOLYET). Venous blood in dif- 

 ferent vascular regions has variable quantities of oxygen. By sum- 

 marizing a great number of analyses by different experimenters, ZUNTZ 

 has calculated that the venous blood of the right side of the heart con- 

 tains on an average 7.15 per cent less oxygen than the arterial blood. 



The quantity of carbon dioxide in the arterial blood (of dogs) is about 

 40 vols. per cent (LUDWIG, SETSCHENOW, PFLUGER, P. BERT, BOHR 

 and HENRIQUES and others), or a little above. In herbivora and the 

 above-mentioned birds the quantity of carbon dioxide in the arterial 

 blood is higher than in the carnivorous dog. SETSCHENOW found 40.3 

 vols. per cent in human arterial blood. The quantity of carbon dioxide 

 in venous blood varies still more (LUDWIG, PFLUGER, and their pupils, 

 P. BERT, MATHIEU and URBAIN, and others). According to the calcula- 

 tions of ZUNTZ, the venous blood of the right side of the heart contains 

 about 8.2 per cent more carbon dioxide than the arterial. The average 

 amount may be put down as 50 vols. per cent. HOLMGREN found in 

 blood after asphyxiation even 69.21 vols. per cent carbon dioxide. 1 



1 All the figures given above may be found in Zuntz's " Die Gase des Blutes " in 

 Hermann's Handbuch d. Physiol., 4, Thl. 2, 33-43, which also contains detailed state- 

 ments and the pertinent literature, and Bohr in Nagel's Handbuch der Physiologic des 

 Menschen, Bd. 1, Hefte 1, 1905, and in Loewy, Handb. d. Bioch. of C. Oppenheimer, 

 Bd. 4. 



