GRADES OF ORGANIC ASCENT. 421 



sumed in their elevation is given forth in the form of heat 

 and organizing force (as is specially seen in germination), 

 which help to raise the portion a to a higher level. But by 

 far the larger part (c) of the organic compounds generated 

 by plants remains stored up in their fabric, without undergo- 

 ing any further elevation ; and it is at the expense of these, 

 rather than of the actual tissues of plants, that the life of 

 animals is sustained. 



When, instead of yielding up any portion of its substance 

 for the sustenance of animals, the entire vegetable organism 

 undergoes retrograde metamorphosis, it not only gives back 

 to the inorganic world the binary compounds from which it 

 derived its own constituents, but in the descent of the several 

 components of its fabric to that simple condition whether by 

 ordinary combustion (as in the burning of coal) or by slow 

 decay it gives out the equivalents of the light and heat by 

 which they were elevated in the first instance. 



In applying these views to the interpretation of the phe 

 nomena of animal life, we find ourselves, at the commence- 

 ment of our inquiry, on a higher platform (so to speak) than 

 that from which we had to ascend in watching the construc- 

 tive processes of the plant. For, whilst the plant had first 

 to prepare the pabulum for its developmental operations, the 

 animal has this already provided for it, not only at the ear- 

 liest phase of its development, but during the whole period 

 of its existence ; and all its manifestations of vital activity 

 are dependent upon a constant and adequate supply of the 

 same pabulum. The first of these manifestations is, as in the 

 plant, the building-up of the organism by the appropriation 

 of material supplied from external sources under the directive 

 agency of the germ. The ovum of the animal, like the seed 

 of the plant, contains a store of appropriate nutriment pre- 

 viously elaborated by the parent ; and this store suffices for 

 the development of the embryo, up to the period at which it 

 can obtain and digest alimentary materials for itself. That 



