Ventilation and Oxygen in the Venous Blood of Man. 551 



Cubic Centimetres Oxygen. 



22 9 "5 resting, breathing air quietly. 



22 • 11 "8 resting, breathing oxygen quietly. 

 7 5 '7 working, breathing air quietly. 



7 5 "6 working, breathing oxygen quietly. 



3 7 '9 resting, breathing air quietly, arm not warmed. 



3 12 - 7 resting, breathing air quietly, arm warmed (to produce vaso-dilatation). 



3 12 '7 resting, breathing oxygen quietly (2), air forcibly (1) ; arm not warmed. 



3 14 "2 resting, breathing oxygen quietly (2), air forcibly (1) ; arm warmed. 



13 13 "5 resting, breathing air forcibly. 



8 13 - 6 resting, breathing oxygen forcibly. 



Oar subjects were medical students and laboratory servants. Some of them, 

 when lying on the couch and breathing quietly, gave us low, and some high 

 readings. The difference is an individual one, and cannot be ascribed to errors 

 in technique, for he who gives a low reading when resting gives a low reading 

 when working. Moreover the deep breathing readings are uniformly high. 

 Some of our subjects were emotionally affected by the operative procedure 

 and breathed about 10 litres a minute, while others breathed only 5-6 litres, 

 while resting on the couch. We cannot, however, ascribe the higher reading 

 in all cases to the ampler breathing. All we can affirm is that quiet 

 breathing gives us a certain proportion of low readings in the given number 

 of subjects, while deep breathing gives us uniformly high readings. 



Looking at the difference between the average figures for resting and 

 breathing air quietly and breathing oxygen quietly it might be assumed that 

 this was due to the oxygen simply dissolved in the blood according to 

 the law of partial pressures. If pure oxygen were breathed we might 

 expect a little over 2 per cent. O2 to be simply dissolved, and the tissues, 

 using this oxygen first, would dissociate the haemoglobin less by the same 

 amount. 



The subjects were breathing not 100 per cent, but about 80 per cent, of 

 oxygen, so the amount simply dissolved would not be quite as much as 

 2 per cent. When, however, we compare the figures obtained during 

 forcible breathing of air or oxygen, we see no evidence of any excess of 

 oxygen due to simple solution under the increased partial pressure of 

 this gas. 



Similarly in a very careful series of analyses of cat's blood recorded by 

 Buckmaster and Gardner and obtained by means of the Topler pump we see 

 no evidence of any increase in oxygen of the arterial blood due to the 

 breathing of oxygen in place of air. The average of 13 analyses, the cats 

 breathing air, was 14 - 2 per cent., breathing oxygen 14'9 per cent. 



No. of 

 analyses. 



