DR. DAVY'S ACCOUNT OF SOME EXPERIMENTS ON THE BLOOD. 289 



further absorption. The tube was transferred to lime-water and agitated ; the resi- 

 dual air was not diminished ; it amounted to thirteen or fourteen measures (the froth 

 prevented precision in marking- the quantity), which possessed the properties of 

 oxygen, as tested by the taper. 



To twenty-eight measures of venous blood of a Sheep, which had absorbed twenty- 

 six of carbonic acid, forty-nine of oxygen were added in the graduated tube over mer- 

 cury: after agitation the blood had acquired the florid arterial hue, and there appeared 

 to be an expansion of one measure. Transferred to lime-water there was an absorp- 

 tion of one or two measures, and no more. 



I shall notice one experiment more, in which blood nearly saturated with carbonic 

 acid was exposed to oxygen, a membrane intervening. Forty-seven measures of 

 venous blood, which had absorbed thirty-three of carbonic acid, were introduced into 

 a glass tube half an inch in diameter, closed at one end with gold-beater's skin, and 

 when filled with blood at the other end also, it was placed over mercury in a small 

 receiver, and thirty-seven measures of oxygen were added to it, under a diminished 

 pressure of about one inch. After twenty-four hours there was no change of volume; 

 the blood in the tube had acquired throughout the arterial hue ; the gas, thirty- 

 eight measures, transferred to lime-water and agitated, diminished to thirty-two. 



The tube was now placed under a receiver, and the air exhausted by the air-pump; 

 a good deal of air was disengaged in the form of froth, and the gold-beater's skin 

 was so distended that it appeared ready to burst ; after three or four minutes air 

 was re-admitted ; a notable portion of gas was found free between the membrane and 

 blood; thus showing that in oxygen gas carbonic acid gas is less freely exhaled 

 through a membrane than in vacuo. 



The results of this second set of experiments are in accordance with those of the 

 first. The inference I am induced to draw from both is rather of a negative kind, 

 and unfavourable to the conclusion of Dr. Stevens already referred Xo, at least in a 

 strict and general sense. I think it right to express myself thus reservedly, reflecting 

 on some of the experiments in which a very little carbonic acid gas appeared to be 

 extricated on agitating blood with hydrogen ; and believing that Dr. Stevens, and 

 other able inquirers, could not have been misled on a point so little exposed to fal- 

 lacy. 



Relative to the eff*ects which Dr. Stevens refers to the attraction of one gas for 

 another, they appear to me, from what I have witnessed in carrying on the inquiry, 

 to admit of explanation on Dr. Dalton's theory of mixed gases, and that in no in- 

 stance is the effect of disengagement of air from a fluid, agitated with another kind 

 of air, greater than were it agitated in a vacuum. 



III. What is the condition of the alkali in the blood in relation to carbonic acid? 



On this point much difference of opinion exists amongst inquirers ; some believing 

 that the alkali, or at least a portion of it, is uncombined, or combined merely with 

 water, or with water and albumen; some that it is united to carbonic acid in the 



MDCCCXXXVIII. 2 p 



