THEORY OF RESPIRATION. 271 



tion of carbonic acid, the amount of this latter gas 

 expired will correspond exactly with that which has 

 been formed ; less, however, will be given out after 

 the use of fat and of still wines, than after cham- 

 pagne. 



According to the views now developed, the glo- 

 bules of arterial blood, in their passage through the 

 capillaries, yield oxygen to certain constituents of 

 the body. A small portion of this oxygen serves to 

 produce the change of matter, and determines the 

 separation of living parts and their conversion into 

 lifeless compounds, as well as the formation of the 

 secretions and excretions. The greater part, how- 

 ever, of the oxygen is employed in converting into 

 oxidised compounds the newly formed substances, 

 which no longer form part of the living tissues. 



In their return toAvards the heart, the globules 

 which have lost their oxygen combine with carbonic 

 acid, producing venous blood ; and, when they reach 

 the lungs, an exchange takes place between this 

 carbonic acid and the oxygen of the atmosphere. 



The organic compound of iron, which exists in 

 venous blood, recovers in the lungs the oxygen it 

 has lost, and, in consequence of this absorption of 

 oxygen, the carbonic acid in combination with it is 

 separated. 



All the compounds present in venous blood, which 

 have an attraction for oxygen, are converted, in the 

 lungs, like the globules, into more highly oxidised 

 compounds ; a certain amount of carbonic acid is 



