OF THE BESPIBATION. 71 



tion, induced Lavoisier to conjecture them to be almost 

 identical processes ; in both, the oxygen disappears, carbonic 

 acid gas is formed, and heat is disengaged. 



But this theory must be abandoned, as opposed to subse- 

 quent experiments and facts ; carbonic acid gas exists already 

 formed in the blood, and is simply exhaled from the surface 

 of the vessels, whilst the oxygen is absorbed into the blood, 

 to be dissolved in it, and to bestow on its particles their living 

 qualities, characteristic of arterial blood. 



123. A simple experiment, made by William Edwards, 

 suffices to place this matter in a clear light. Place in a close 

 vase filled with nitrogen or azote, a frog ; in this gas the frog 

 can live for a considerable time. Now analyze it, and you 

 will find that, although deprived of oxygen, the animal con- 

 tinues to give out carbonic acid gas. There can then be no 

 combustion, as Lavoisier supposed. 



124. In fact, the blood always contains carbonic acid 

 gas dissolved in it ; and Magnus has shown that the blood 

 can dissolve a certain measure of any gas with which it may 

 be' brought in contact by giving out a portion of the gas 

 first absorbed when dissolving a portion of the second. 

 Thus, by agitating blood in hydrogen, a certain amount of gas 

 is absorbed, and a certain quantity of carbonic acid gas is set 

 free. The same happens when oxygen is used instead of 

 hydrogen, and the blood assumes an arterial character. 



125. It results, indeed, from numerous experiments, 

 that, as the changes observed to take place during respiration 

 equally happen to blood when contained in a bladder, oxygen 

 disappearing by being absorbed through the walls of the 

 bladder, and carbonic acid gas appearing, which must have 

 come from the blood and equally passed through the walls 

 of the bladder, the phenomena of respiration must in a great 

 measure be chemical, since they take place as well in bl'ood 

 withdrawn from the body as in the pulmonary vessels. 



126. What happens in the respiratory act seems to be as 

 follows : the venous blood coming from all parts of the body 

 reaches the lungs, holding in solution a considerable amount 

 of carbonic acid gas, a little azote, and some traces of oxygen. 

 As it passes through the lungs it comes as it were in contact 

 with the air, and dissolves a portion ; oxygen and a certain 

 amount of nitrogen are thus absorbed, and these gases by 

 being thus taken into the blood, expel a certain amount of 

 carbonic acid gas and of azote ; the carbonic acid gas exhaled 



