IN THE ANIMAL ORGANISM. 231 



tion of heat and of force may seem to be connected 

 together, with reference to mechanical effects, yet the 

 disengagement of heat can in no way be considered as 

 in itself the only cause of these effects. 



All experience proves, that there is, in the organism, 

 only one source of mechanical power ; and this source 

 is the conversion of living parts into lifeless, amor- 

 phous compounds. 



Proceeding from this truth, which is independent of 

 all theory, animal life may be viewed as determined by 

 the mutual action of opposed forces ; of which one 

 class must be considered as causes of increase (of sup- 

 ply of matter), and the other as causes of diminution 

 (of waste of matter) . 



The increase of mass is effected in living parts by 

 the vital force ; the manifestation of this power is de- 

 pendent on heat ; that is, on a certain temperature 

 peculiar to each specific organism. 



The cause of waste of matter is the chemical action 

 of oxygen ; and its manifestation is dependent on the 

 abstraction of heat as well as on the expenditure of the 

 vital force for mechanical purposes. 



The act of waste of matter is called the change of 

 matter ; it occurs in consequence of the absorption of 

 oxygen into the substance of living parts. This absorp- 

 tion of oxygen occurs only when the resistance which 

 the vital force of living parts opposes to the chemical 

 action of the oxygen is weaker than that chemical ac- 

 tion ; and this weaker resistance is determined by the 



