IN THE ANIMAL ORGANISM. 201 



self endanger the existence of the living part, because 

 the opposing forces would be left in equilibrio ; but, by 

 the removal of the excess of force, the part would lose 

 its capacity of growth, its power to cause further de- 

 compositions, and its ability to resist external causes of 

 change. If, in this state of equilibrium, oxygen (a 

 chemical agent) should be brought in contact with it, 

 then there would be no resistance to the tendency of 

 the oxygen to combine with some element of the living 

 part, because its power of resistance has been taken 

 away by some other application of its excess of vital 

 force. According to the amount of oxygen brought to 

 it, a certain proportion of the living part would lose its 

 condition of vitality, and take the form of a chemical 

 combination, having a composition different from that 

 of the living tissue. In a word, there would occur a 

 change in the properties of the living compound, or 

 what we have called a change of matter. 



If we reflect that the capacity of growth or increase 

 of mass in plants is almost unlimited ; that a hundred 

 twigs from a willow tree, if placed in the soil, become 

 a hundred trees ; we can hardly entertain a doubt, that 

 with the combination of the elements of the food of 

 the plant so as to form a part of it, a fresh momentum 

 of force is added in the newly formed part to the pre- 

 viously existing momentum in the plant ; insomuch, that 

 with the increase of mass, the sum of vital force is 

 augmented. 



According to the amount of available vital force, the 



