THE BLOOD. 101 



of about 75-80 mm. mercury. BOHR has obtained a somewhat differ- 

 ent result from his investigations. He experimented on dogs 

 which were injected with leech infusion or peptone solution so as 

 to prevent coagulation of the blood, and he allowed the blood to 

 circulate through an apparatus which was inserted between the 

 central and peripheral end of the cut carotid, or between the cen- 

 tral end of the carotid and the central end of the cu t jugular vein, 

 and in this way the exchange of gases between the blood and a gas 

 mixture of known constitution could be determined. As measure 

 of the tension of the oxygen in the arterial blood he obtained a dis- 

 proportionate high value or an average pressure of 136.5 mm. mer- 

 cury. By a simultaneous determination of the oxygen tension in 

 the blood and in the expired air of the same animals he found in 

 several cases a higher value for the former than for the latter. 

 While according to P. BERT'S investigations the taking up of oxy- 

 gen from the air of the lungs by the blood may be explained by the 

 high oxygen partial pressure in the air of the lungs, this is not per- 

 ceptible according to the experiments of BOHR, in which the ten- 

 sion of the oxygen in the blood is greater than in the expired air, 

 and also for evident reasons it is still greater than in the alveolar 

 air. BOHR is also of the opinion that the generally-accepted diffu- 

 sion theory does not give sufficient explanation for the taking up 

 of oxygen from the air, and that we must also admit that the lung- 

 tissue itself plays an active part in the taking up of oxygen. 



As the chief quantity of the oxygen in the blood simply ab- 

 sorbed, corresponding to the pressure, is contained as a loose chem- 

 ical combination, it is to be supposed that the amount of oxygen in 

 the blood, at least within certain limits, is independent of the 

 amount of oxygen in the air. 



That the raising of the oxygen pressure, even to a pressure of 

 one atmosphere, has no essential influence on the amount of oxygen 

 taken up, and on the carbon dioxide eliminated, has been known 

 for a long time (LAVOISIER, EEGNAULT, and EEISET). Further 

 experiments in this direction have been made by PAUL BERT. He 

 found that in pure oxygen at a pressure of 3 atmospheres, or in or- 

 dinary air at a pressure of 15 atmospheres, animals quickly died 

 with convulsions. Before and during the spasms a lowering of 

 temperature took place, and the consumption of oxygen, as well as 



