SECRETION AND ABSORPTION OF GAS, ETC. 243 



siderably lower than those usually found by Bohr, and were 

 also lower than in expired air. His conclusion is that dif- 

 fusion explains the exchange of gases between the blood 

 and the air of the lungs, but that in the case of oxygen 

 there is not time for the tensions in the blood and alveolar 

 air to equalise themselves. Thus, to take an example, in 

 experiment 5 a tension of 2*45 per cent, of carbonic acid 

 (maximum value) was found in the arterial blood. Hence 

 the percentage of carbonic acid in the alveolar air would be 

 2*45 per cent., and the corresponding alveolar-oxygen ten- 

 sion about 1 8 per cent. The oxygen tension actually found 

 in the blood was only, however, 9*29 per cent, (maximum 

 value). Hence equilibrium had not nearly established 

 itself between the oxygen tensions in the blood and alveolar 

 air. In a further series of experiments, 1 in which the animal 

 breathed nearly pure oxygen, the difference between the 

 tension of oxygen in the arterial blood and that calculated 

 on the diffusion theory for the alveolar air from the carbonic- 

 acid tension was still greater. Thus with 84*6 per. cent, of 

 oxygen in the inspired air an oxygen tension of 56*2 per 

 cent, and a carbonic-acid tension of 5 per cent, were found 

 in the arterial blood. On the diffusion theory supported 

 by Fredericq the oxygen tension of the arterial blood must 

 thus have been 22 per cent, of an atmosphere below that of 

 the alveolar air. 



In addition to Fredericq's own experiments a further 

 series from his laboratory were recently published by Weis- 

 berger. 2 The animal breathed into and out of a large bag. 

 The bag and the aerotonometer were filled with the same 

 gas mixture, and at the end the gas in the bag and in the 

 aerotonometer was again analysed. The results were that 

 as regards carbonic acid the gas in the aerotonometer at the 

 end of the experiment in five cases contained from "66 to 

 275 per cent, more carbonic acid than the air of the bag, 

 and in six cases from 3*36 to *i8 per cent, less carbonic acid. 

 As regards oxygen in three cases there was from 12*3 to 

 47 per cent, less oxygen in the aerotonometer, and in six 



1 Arch. d<? Biologie, 1896. 2 Ibid. 



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