DR. DAVY'S ACCOUNT OF SOME EXPERIMENTS ON THE BLOOD. 297 



the blood, not capable of being extracted by the air-pump, and yet capable of enteiv 

 ing into combination with nitrous gas, and which exists in largest proportion in arte- 

 rial blood ? Unless this conclusion is adopted, it must be supposed either that the 

 nitrous gas which disappears is decomposed, or that it combines directly with the 

 red particles ; neither of which suppositions is well supported by facts. The cir- 

 cumstance that no azote is disengaged, is not favourable to the idea that the nitrous 

 gas is decomposed ; and the difference of effect in the instances of venous and arte- 

 rial blood, and, after and before agitation with oxygen, is not in accordance with the 

 notion of direct combination. I may mention another fact which seems to have the 

 same bearing : serum, which does not absorb oxygen, I find also does not absorb ni- 

 trous gas, excepting in about the proportion in which water absorbs it : and, further, 

 in corroboration, I may mention, that as blood putrefies, whether arterial or venous, 

 its power of absorbing nitrous gas diminishes ; and that it is also diminished by be- 

 ing agitated with phosphuretted hydrogen. Thus the arterial blood of a Sheep, which 

 before agitation with phosphuretted hydrogen absorbed 45*3 per cent, of nitrous gas, 

 after agitation with it absorbed 7'4 per cent, less ; and, after it had become putrid, it 

 absorbed twenty per cent. less. According to my observations, arterial blood does 

 not lose its peculiar florid hue under the action of the air-pump. Is not this also in 

 favour of the above inference, that a portion of oxygen is retained by the blood re- 

 sisting extraction by the air-pump? I find also that when venous blood is agitated 

 with oxygen and subjected to the air-pump, it, in like manner, retains its acquired 

 florid vermilion hue, and likewise a power of absorbing an additional quantity of ni- 

 trous gas. 



VII. When oxygen is absorbed by the blood is there any production of heat 9 

 To endeavour to determine this point, of so much interest in connexion with the 

 theory of animal heat, a very thin vial, of the capacity of eight liquid ounces, was se- 

 lected and carefully enveloped in bad conducting substances, viz. several folds of 

 flannel, of fine oiled paper, and of oiled cloth. Thus prepared, and a perforated cork 

 being provided, holding a delicate thermometer, two cubic inches of mercury were 

 introduced, and immediately after it was filled with venous blood, kept liquid as be- 

 fore described. The vial was now corked and shaken ; the thermometer included 

 was stationary at 4.5°. After five minutes that it was so stationary, the thermometer 

 was withdrawn, the vial closed by another cork was transferred inverted to a mer- 

 curial bath, and 1 J cubic inch of oxygen was introduced. The common cork was re- 

 turned, and the vial was well agitated for about a minute ; the thermometer was now 

 introduced, it rose immediately to 46°, and continuing the agitation it rose further to 

 46*5, very nearly to 47°. This experiment was made on the 12th of last February 

 on the blood of the Sheep. 



On the following day a similar experiment was made on the venaus blood of Man. 

 The vial was filled with eleven cubic inches of this blood, its fibrin broken up in the 

 usual manner, and with three cubic inches of mercury; the temperature of the blood 



MDCCCXXXVIII. 2 Q 



