OXYGEN, FIBRINE, AND ALBUMEN. 173 



to change their colour, and to assume the dark red 

 colour 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 arterialised globules of the oxygen 

 which they have absorbed from the air ; and we 

 can draw no other conclusion from the change of 

 colour which occurs in the capillaries, than that the 

 arterialised globules, during their passage through 

 the capillaries, return to the condition which cha- 

 racterized them in venous blood ; that, consequently, 

 they give up the oxygen absorbed in the lungs, and 

 thus acquire the powder of combining with that 

 element afresh. 



78. We find, therefore, in arterial blood, albu- 

 men, wdiich, like all the other constituents of that 

 fluid, has become saturated with oxygen in its pas- 

 sage through the lungs, and oxygen gas, which is 

 conveyed to every particle in the body in chemical 

 combination with the globules of the blood. As 

 far as our observations extend (in the developement 

 of the chick during incubation), all the conditions 

 seem to be here united which are necessary to the 

 formation of every kind of tissue ; w^hile that por- 

 tion of oxygen which is not consumed in the growth 

 or reproduction of organs combines with the sub- 

 stance of the living parts, and produces, by its 

 union with their elements, the act of transforma- 

 tion which we have called the change of matter. 



