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SCIENCE PROGRESS. 



cases from 4*35 to # o8 per cent, more oxygen. In no case 

 was there less carbonic acid or more oxygen in the aeroto- 

 nometer at the end than at the beginning of the experiment. 

 Weisberger considers that the results support the diffusion 

 theory, and explains the higher percentages of oxygen and 

 lower percentages of carbonic acid in the aerotonometer at 

 the end of most of the experiments on the theory that the 

 changes of composition in the air of the aerotonometer oc- 

 curred so slowly that they lagged behind those of the bag. 

 This explanation is quite a probable one, but it is evident 

 that the results are not such as to add any very distinct 

 support to the diffusion theory. 



Fredericq's experiments were much longer than those of 

 Bohr, so as to allow of sufficient time for equilibrium to 

 establish itself between the gas tensions in the blood and the 

 air of the aerotonometer. He calls special attention to the 

 extreme slowness with which equilibrium establishes itself 

 as regards oxygen tension, and criticises Bohr's experiments 

 on the ground that the latter frequently did not allow suffi- 

 cient time for this to occur. That such was the case in 

 many of the experiments cannot be denied. It is neverthe- 

 less impossible to explain away Bohr's conclusions simply on 

 this ground, as in certain experiments the oxygen in the 

 aerotonometer air was found to have risen to a higher per- 

 centage than in the expired air, or the carbonic acid in the 

 aerotonometer had fatten to a lower point than in the ex- 

 pired or tracheal air, or even, in one case, than in the in- 

 spired air. The results of the experiments in question may 

 be quoted here. 



