DR. DAVY'S ACCOUNT OF SOME EXPERIMENTS ON THE BLOOD. 295 



of arterial blood for oxygen, before and after exhaustion by the air-pump, as a further 

 test experiment, whether arterial blood contain oxygen in a free state, that is, admit- 

 ting of being extricated by the removal of atmospheric pressure. The result of this 

 trial also has been negative ; its power of absorbing oxygen has not appeared to be 

 at all increased by exhaustion ; this at least was the result of one experiment carefully 

 conducted. 



VI. Is any oocygen contained in the blood not capable of being extricated by the air- 

 pump ? 



Before I was acquainted with the researches of M. Magnus I had instituted some 

 experiments to endeavour to determine whether any oxygen in a free state, or in a 

 condition approximating to that state, exists in the blood, and especially in the arte- 

 rial, admitting of being detected by means of substances possessing a strong attrac- 

 tion for oxygen, or of being expelled by substances of greater solubility in blood than 

 oxygen. Hydrogen, phosphuretted hydrogen, sulphuretted hydrogen, nitrous oxide 

 and nitrous gas, it appeared advisable to try, as belonging to the first class of sub- 

 stances, and carbonic acid gas as belonging to the latter. 



The results with hydrogen, sulphuretted hydrogen, nitrous oxide and carbonic acid 

 gas, were of a negative kind. Neither using arterial blood, nor blood which had 

 been agitated with oxygen, and which had absorbed or made to disappear a certain 

 quantity of this gas, could I detect any indications of its presence either by combi- 

 nation or expulsion. In the instances of nitrous oxide and carbonic acid, however, 

 it may be worthy of remark, that the blood which had been agitated with oxygen 

 absorbed less of either of these gases than it did before it was so treated*. 



The results with phosphuretted hydrogen, the spontaneously inflammable species, 

 were of an ambiguous kind, not sufficiently clear to deduce from them any satisfac- 

 tory conclusion. In one trial, serum of the venous blood of the Sheep absorbed nine 

 per cent, of this gas ; venous blood ITS per cent. ; and arterial 5'8 per cent-}-. 



The results with nitrous gas were of a different kind, and may be deserving of be- 

 ing specially noticed. 



The blood used was that of the Sheep prepared in the usual manner. The expe- 

 riments were made during the very cold weather which prevailed in the beginning of 

 the year, and the difference of colour between the venous and arterial blood was very 

 strongly marked. 



* Nitrous oxide I find is absorbed in about the same proportion by venous and arterial blood, and by the 

 serum of blood, and also in about the same proportion by water. Thus, at the temperature of 45" over mer- 

 cury, using the blood and serum of the same animal (the Sheep), thirty-two measures of each absorbed twenty- 

 two measures of this gas, and thirty-two of distilled water absorbed 2\'b. 



t Supposing the gas decomposed, the phosphorus uniting with the oxygen in the blood, the apparent smaller, 

 absorption by arterial than by venous blood is what might be expected, on the idea that the former kind of 

 blood contains most oxygen. 



