212 THE PHENOMENA OF MOTION 



combination with the substance of the organ which has 

 lost the vital force ; and a corresponding proportion of 

 the substance of the organ is separated from the living 

 tissue in the shape of an oxidized compound. 



All those parts of the body which nature has des- 

 tined to effect the change of matter, that is, to the pro- 

 duction of mechanical force, are penetrated in all direc- 

 tions by a multitude of the most minute tubes or vessels, 

 in which a current of oxygen continually circulates, in 

 the form of arterial blood. To the above-mentioned 

 separation of part of the elements of these parts, in 

 other words, to the disturbance of their equilibrium, this 

 oxygen is absolutely essential. 



As long as the vital force of these parts is not con- 

 ducted away and applied to other purposes, the oxygen 

 of the arterial blood has not the slightest effect on the 

 substance of the organized parts ; and in all cases, only 

 so much oxygen is taken up as corresponds to the con- 

 ducting power, and, consequently, to the mechanical 

 effects produced. 



The oxygen of the atmosphere is the proper, active, 

 external cause of the waste of matter in the animal 

 body ; it acts like a force which disturbs and tends to 

 destroy the manifestation of the vital force at every 

 moment. But its effect as a chemical agent, the dis- 

 turbance proceeding from it, is held in equilibrium by 

 the vital force, which is free and available in the living 

 tissue, or is annihilated by a chemical agency opposed 



