1835.] Researches on the Blood. 57 



On the other hand, Darwin could detect no such acid, 

 and Dr. Davy asserts that it is neither extracted during the 

 spontaneous coagulation of the blood, nor by the air pump, 

 nor by coagulating the serum by heat, and that serum ab- 

 sorbs carbonic acid in greater quantity than pure water, 

 which would not be the case if it was charged with carbonic 

 acid. 



Gmelin and Tiedemann examined with great care the 

 blood of a dog taken from the femoral-vein and artery, and 

 placed in different tubes under the receiver of an air pump. 

 The result was that neither carbonic acid nor any other 

 permanent gas was extricated. To ascertain the accuracy 

 of Davy's statement with respect to the absorbing power of 

 blood being greater than that of water, carbonic acid was 

 allowed to stand over arterial blood for 5 days, when it was 

 ascertained that 100 measures of blood absorb 120 of car- 

 bonic acid. The coagulum appeared blackish red, and the 

 liquid portion was extremely clear. 



Since blood contains no free carbonic acid, it was neces- 

 sary to ascertain whether any existed in it in a combined 

 state. Vinegar was added to each of the kinds of blood 

 which had been collected, as in the former experiments, with 

 every precaution to ensure accuracy, and was placed under 

 a receiver. A quantity of carbonic acid escaped from both, 

 more abundantly from the veinous than the arterial. The 

 arterial blood mixed with vinegar, as well as the veinous 

 blood, left over mercury for 3 weeks, was converted into a 

 blackish brown mass without being separated into serum 

 and coagulum. About the same period, without a know- 

 ledge of the Heidelberg experiments, Ed. Ch. F. Stromeyer 

 obtained the same results.* 



How do these facts agree with the present theories of 

 respiration 1 



Lavoisier conceived that without coming in contact with 

 the respired air, a liquid consisting principally of carbon 

 and hydrogen is absorbed through the pulmonary mem- 

 branes into the bronchi, and is converted into carbonic acid 

 and water through the oxygen of the inspired air. As this 



* Schweigg. Journ. fur Chem. lxiw 105. 



t Memoirs de 1 l'acad des Sc. An. 1790, inserted in Scherer's Journal der Chemie 

 x. 560. 



