170 PHYSIOLOGY AND HEALTH. 



more thorough examination of the" plans of the benevolent 

 Author of all things, shows that there is no natural want 

 without a due supply. And if that want be permanent, the 

 means of gratifying it are equally so, and coextensive w ith it. 

 The works of the Creator are all arranged in infinite wisdom. 

 There is no deficiency there is no want of harmony. 

 The oxygen, which is so continually and universally con- 

 sumed by the animal creation, is restored by agents equally 

 universal and permanent. 



396. Animals and vegetables meet each other's wants, 

 and supply each others necessities. The animal uses oxy- 

 gen, and gives out carbonic acid gas ; while, on the other 

 hand, the plant uses carbonic acid gas, and gives out oxygen. 

 The vegetables, like animals, breathe air; but, unlike them, 

 they breathe it for the carbonic acid, and not for the oxygen. 

 Through the leaves of some, which are provided with them, 

 and through the bark of others, the carbonic acid is absorbed 

 from the air, and then, within this vegetable respiratory ap- 

 paratus, it is decomposed the carbon is retained to nourish 

 the plant, while the oxygen is thrown out for the use of the 

 animated creation. Thus the equilibrium is maintained ; 

 and, as long as both live together, there need be no fear of 

 their suffering for want of air suited to their necessities. 



397. This process of respiration of vegetables is con- 

 ducted only in the presence of light. In its absence, in 

 darkness, precisely the reverse takes place, and the vegetable 

 respiration is similar to that of animals oxygen is ab- 

 sorbed, and carbonic acid given out. 



398. Plants, then, as they aid animal respiration when 

 they have the light of the sun, are proper and healthy accom- 

 paniments of any inhabited room in the daytime. But, on 

 the other hand, as, in darkness, they consume the oxygen 

 that animal respiration needs, they are unhealthy and inju- 

 rious to be kept in rooms which are occupied in the night 

 for sleeping or other purposes. 



