164 ACTION OF ARTERIAL BLOOD. 



all those constituents of the blood, which possess in any 

 degree the power of combining with oxygen, absorb it 

 in the lungs, and become saturated with it. Although 

 in contact with these other compounds, the globules, 

 when arterialized, retain their florid, red color in the 

 most minute ramifications of the arteries ; and we ob- 

 serve them to change their color, and to assume the 

 dark red color which characterizes venous blood, only 

 during their passage through the capillaries. From these 

 facts we must conclude, that the constituents of arterial 

 blood are altogether destitute* of the power to deprive 

 the arterialized globules of the oxygen which they have 

 absorbed from the air ; and we can draw no other con- 

 clusion from the change of color which occurs in the 

 capillaries, than that the arterialized globules, during 

 their passage through the capillaries, return to the con- 

 dition which characterizes them in venous blood ; that, 

 consequently, they give up the oxygen absorbed in the 

 lungs, and thus acquire the power of combining with 

 that element afresh. 



77. We find, therefore, in arterial blood, albumen, 

 which, like all the other constituents of that fluid, has 

 become saturated with oxygen in its passage through 

 the lungs, and oxygen gas, which is conveyed to every 

 particle iri the body in chemical combination with the 

 globules of the blood. As far as our observations ex- 

 tend (in the development of the chick during incuba- 

 tion), all the conditions seem to be here united which 

 are necessary to the formation of every kind of tissue ; 

 while that portion of oxygen which is not consumed in 



