THE RABBIT. 9 



oxidation of the materials which make up its body. So far, 

 the source of the rabbit's energy is clear ; but there must 

 evidently be some means of renewing the complex compounds, 

 or the rabbit's life would soon come to an end. This 

 renewal constitutes nutrition, or feeding. 



14. The Food of Animals. A very considerable portion 

 of the rabbit's daily labour is devoted to obtaining, nibbling 

 up, swallowing, and treating in other less visible ways, 

 portions of the vegetation among which it lives. Indeed, 

 this, along with the endeavour to escape being itself eaten, 

 and its efforts to add as many as possible to the total 

 number of living rabbits, must pretty well exhaust the 

 account of its life-labours. It is from this vegetation that 

 the rabbit obtains the compounds needful for the repair of 

 its body, and also (while growth or reproduction is going 

 on) for the formation of new living substance. Some small 

 portion of the food taken in is passed out again, practically 

 unaltered, in the form of little pellets, the fences : the 

 greater portion, after undergoing various changes, to be 

 described in the next chapter, enters into the formation of 

 new living tissue. Thus the rabbit is dependent on the 

 plant kingdom for the maintenance of its life. So, too, 

 are all animals, directly or indirectly ; for though one 

 animal may feed on another and that in turn on another, 

 this process cannot be carried on indefinitely : sooner or 

 later we must come down to an animal which is a plant- 

 feeder. In the long run all animals are dependent on 

 plants for both the material and the energy of their bodies. 



15. Sources of Material and Energy of Living Things. 



We must trace the supply one stage farther. Whence do 

 plants obtain their material and their energy ? The full 

 answer to this will be found by the reader in his botanical 

 text-book: here we can only point out the most general 

 facts. The source of material is very largely the waste- 

 products of animals carbon dioxide, water, urea (or 

 its decomposition -products), etc. But the mineral kingdom 

 is also largely drawn upon, the decomposition of the rocks 

 of the earth's crust furnishing a great deal of necessary 



