NATURAL HISTORY 



7 



THE FOOD OF ANIMALS 



INTRODUCTORY 



In the early part of Volume I a brief sketch has been given of 

 the process of digestion, by which food is dealt with within the 

 body, and we shall be chiefly concerned in the present section with 

 the various means by which animals obtain the necessary materials 

 wherewith to repair and build up their bodies. Occasion will, 

 however, be taken to recapitulate some of the essential facts and 

 principles relating to the digestive process. 



It has been cynically remarked that life may be summarized in 

 the conjugation of a single verb — the verb " to eat " — in its various 

 moods and tenses: — " I eat, thou eatest, he or she eats ", &c., with 

 the terrible converse, " 1 am eaten, thou art eaten, he or she is 

 eaten", &c. This epigrammatic statement embodies a great deal of 

 truth, for a primary characteristic of living things is the constant 

 necessity for food — the law of hunger. A nugget of gold, or a 

 quartz crystal, may remain for an indefinite time without under- 

 going any appreciable change, and any addition to its substance 

 which may take place consists in the deposition of fresh external 

 layers, such as one sees in the cross-section of a stalactite. But 

 the essential living part of an animal, that exceedingly complex 

 substance known as protoplasm, is extremely unstable, and in- 

 cessantly undergoing waste by a process of breaking down into 

 simpler substances, the simplest of which — as waste products — 

 have to be eliminated from the organism. Every manifestation 

 of life, whether it be a muscular movement, the formation of 

 a digestive fluid, a thought, or an emotion, involves and is 



Vol. II. 1 33 



