RELATIONS OF THE THREE KINGDOMS. 



s 



are incapable of locomotion. What, then, are the dif- 

 ferences ? 



i. Sensation and Volition. — Doubtless conscious 

 sensation and voluntary motion are characteristic of 

 animals, but the difficulty is in applying the test. We 

 conclude, and probably rightly, that the motions of 

 plants are unconscious and involuntary. In the case 

 of any motion, if we could be certain that it was at- 

 tended with consciousness, we would rightly conclude 

 that the moving thing was an animal. But how are we 

 to know ? Very many of the motions of animals, and 

 even motions within our own bodies, such as motions of 

 the heart, stomach, etc., are wholly unconscious and in- 

 voluntary. 



2. Nature of the Food and the Relation to the 

 Mineral Kingdom. — Plants feed on the mineral king- 

 dom directly ; animals feed on plants or on one another. 

 The food of plants is mineral matter ; the food of animals 

 is organic matter made by plants. More specifically, 

 the food of plants is CQ 3 .H 2 and NH 3 . These purely 

 mineral matters are taken 

 and decomposed. Some ; Hr _,. ,, ; . 



parts are thrown away, and 

 the remainder are made 

 to combine into new sub- 

 stances not made elsewhere 

 ■ — i. e., organic substances, 

 such as starch, sugar, cellu- 

 lose, and especially proto- 

 plasm. Thus all the or- 

 ganic substance in the world 

 is created by plants, under 

 the influence of sunlight. Animals, so far from creating, 

 are constantly destroying organic matter and resolving 

 it into its original components. Thus the relations of 



Fig. 2. — Diagram illustrating: the 

 circulation of carbon and oxygen. 



