DR. DAVY'S ACCOUNT OF SOME EXPERIMENTS ON THE BLOOD. 285 



also had been washed with lime-water. After an absorption equal to about one cubic 

 inch, some of the air was passed into lime-water : it occasioned a just perceptible 

 cloudiness ; and eighty measures of it agitated with lime-water were reduced hardly 

 to 79-5. 



Taking it for granted that this very minute quantity of carbonic acid derived from 

 the blood existed in the state of gas, and not contained in the aqueous vapour, as is 

 possible, it is matter for consideration from whence it was derived, — whether it was 

 formed at the moment by the action of the air on the blood, or, previously existing 

 in the blood, was now merely expelled. Further on I propose to return to this im- 

 portant question. 



When I reflect on the results stated above relative to the absorption or disap- 

 pearance of oxygen, and compare them with those alluded to formerly obtained, I 

 am not a little surprised at their discrepancy ; and I can only account for it by sup- 

 posing that it may have been owing in part to the difference of season when the two 

 sets of experiments were conducted. The first were made in Malta in 1829, in the 

 hot months of July and August, when the thermometer in the open air was generally 

 above 80*^ and occasionally above 90°. The last have been made in England, and 

 principally in January of the present year, when the temperature of atmosphere was 

 occasionally low, the greater part of the time below the freezing point, and often as 

 low as 20°. From what I have witnessed, I am induced to infer, that the higher the 

 atmospheric temperature is, and the less necessity there is for the production of ani- 

 mal heat, the less difference there is between venous and arterial blood, and the less 

 power the former has of combining with oxygen and of forming or evolving carbonic 

 acid. In Malta I carefully compared the blood of the jugular vein and carotid artery 

 of a Sheep during the season mentioned ; when coagulated and still hot, there was 

 no perceptible difference in their colour ; in each it was less florid than the arterial 

 blood of the same animal in England in winter, and less dark than the venous : its 

 hue was as it were a mixture of the two. And in this observation I could not be 

 mistaken; the circumstances under which it was made precluded mistake; vessels of 

 the same size were used ; similar quantities of blood were introduced, and they were 

 seen in the same light side by side. And in confirmation of this view 1 may remark, 

 that during the last winter, when the cold was unusually severe, I found the tempe- 

 rature of deeply seated parts, and especially of the heart and its left ventricle, in the 

 instance of Sheep, unusually high: the mean of nine observations on the tempe- 

 rature of the left ventricle in different animals was 107'5 ; the lowest was 105*5 ; the 

 highest 109' ; whilst the temperature of the rectum (the mean of the same number of 

 observations) was 104*4. 



II. Does the blood, especially venous blood, contain carbonic acid capable of being 

 expelled by agitation with another gas, as hydrogen or orygen P 



In a paper published in the Philosophical Transactions for 1832, Dr. Stevens has 

 answered this question in the affirmative : he maintains that carbonic acid gas exists 



