502 



RESPIRATION 

 100 C.C. OF ARTERIAL BLOOD CONTAIN: 



A difference of 9 per cent, was frequently encountered, dependent 

 entirely upon the speed of the extraction of the gases; in fact, inas- 

 much as the oxidations continue for some time after the blood has 

 been removed, a greater yield of carbon dioxid is generally obtained 

 than would be, if these processes could be made to cease immediately. 

 But naturally, this oxidation is restricted to the formed elements of 

 the blood, for the very obvious reason that their metabolism does not 

 cease directly after their escape from the circulation. 



The observations of Setschenow upon blood withdrawn directly 

 from the arteries of man have given 21.6 c.c. of oxygen, 40.3 c.c. of 

 carbon dioxid and 1.6 c.c. of nitrogen for each 100 c.c. of blood. Argon 

 is present in very insignificant amounts, its exact value being about 

 0.04 volume per cent. Traces of hydrogen and carbon monoxid may 

 also be present, the former being derived from the intestinal canal 

 and the latter from the air. Thus, it may be said, in a general way, 

 that 100 c.c. of arterial blood yield about 60 c.c. of a mixture of gases. 

 In the venous blood of the dog the oxygen varied between 5.5 and 

 16.6 c.c. and the carbon dioxid between 38.8 and 47.5 c.c. If the aver- 

 age values of these determinations, namely 11.9 c.c. and 44.3 c.c. 

 respectively, are now compared with the figures given above, the fol- 

 lowing averages are obtained for each 100 c.c. of blood at C. and 

 under a pressure of 760 mm. Hg: 



Arterial blood 20 c.c. O 2 



Venous blood 8-12 c.c. O 2 



40 c.c. CO 2 1-2 c.c. N 

 46-50 c.c. CO 2 1-2 c.c. N 



The Condition of Oxygen in the Blood. The plasma of the blood 

 is a watery solution containing 9 per cent, of solids, whereas its formed 

 elements embrace 40 per cent, of solids. At this time, attention 

 should again be called to the fact that the absorption of oxygen by the 

 blood is different from that of oxygen by water, because this gas enters 

 into a chemical combination with the hemoglobin of the red cells. 

 Normal blood, as we have just seen, contains about 20 volume per cent. 



