396 



to lay before the Koyal Society an account of that part of his 

 researches which relates to the cause of the change of colour 

 of the blood in its passage through the lungs, he had pre- 

 pared and nearly completed the paper on this subject, of which 

 the following is a shoi't abstract. It may be proper to state 

 that no reference is made in the paper to the recent experi- 

 ments of Magnus, which are now generally held to afford in- 

 controvertible proof of the existence of free carbonic acid in 

 greater, and of oxygen in less quantity, in venous than in 

 artei'ial blood. These experiments came to be known in this 

 country only a short time before Mr Ellis's death, and, had 

 he been acquainted with them, might have tended to modify 

 his views.] 



In the first part of the paper, the author states that he still main- 

 tains the opinion expressed in his published work on respiration, 

 viz., that the quantity of carbonic acid formed in respiration is ex- 

 actly equal to that of the oxygen consumed ; and he enters into a de- 

 tailed critical analysis of the different experiments recorded by 

 authors on this subject, placing, however, his chief reliance upon 

 those of Bei-thollet, and of Allen and Pepys, in order to justify his 

 opinion. He also holds the view that the exhalation of carbonic 

 acid and consumption of oxygen are not independent processes, but 

 are the immediate result of the direct union of carbonic and oxygen 

 within the air-cells of the lungs, and he expresses doubts as to the 

 accuracy of the experiments of Edwards, which have by many been 

 held to establish the opposite view. 



Proceeding upon this basis, the author next examines the effects 

 of air and other re-agents upon blood out of the body, and deduces 

 the conclusion, that, although oxygen gas appears to have the direct 

 effect of changing the colour of the blood from dai'k to bright red, 

 that change may be induced without the presence of any oxygen gas, 

 and that within the living body, it is not necessary to attribute the 

 change to the agency of that gas. In proof of this, the author refers 

 particularly to the experiments of Stevens and of Gregory, and he also 

 details experiments made by himself, which shew that, while a strong 

 saline fluid has of itself the power of changing the colour of the blood, 

 weaker saline solutions, or such as contain no more salt than is na- 

 turally dissolved in the serum of the blood, do not effect any change 

 unless oxygen gas be also present ; and that water, which contains 

 dissolved in it less than y-^g part of its weight of salt, does not 

 brighten blood even in air. 



