SOILS AND FERTILIZERS. 397 



of allowing some one with peculiar facilities for performing an act 

 to do that exclusively, that others may profit by his skill. So long as 

 each man sought and killed his food, cooked his meals, made his own 

 clothing, weapons, and implements — in a word, lived alone — advance 

 was impossible. It was only when he who was most skillful with the 

 needle made garments for the hunter in exchange for a haunch of 

 venison, that the hunter could practice marksmanship, and the tailor 

 design a new cut for the mantle with which the warrior might dazzle 

 the daughter of the arrow maker. It is the same in Nature. Some 

 organisms possess powers of elaborating certain materials of which 

 others are quick to avail themselves. Plants can manufacture starch, 

 an article needed by animals, but of which their own capacity, so far 

 as producing it is concerned, is very limited, and thus animals find it 

 advantageous to avail themselves of these stores instead of taxing 

 their own resources. Similarly, plants need the organic matters of 

 the animal bodies, and wise agriculture supplies carbon, nitrogen, and 

 other articles of food in the shape of animal and vegetable refuse. 

 But this matter requires digestion; it must be made soluble before it 

 can be absorbed, and but few plants can effect this solution unaided. 

 The " Venus's flytrap," the sundew, the wonderful " carrion plant," 

 and others, are equipped Avith elaborate apparatus by which they are 

 enabled to capture, kill, and literally digest the insects that supply 

 them with nitrogeneous food, but these are exceptional cases. Na- 

 ture usually employs other agents. 



The action of bacteria in causing decay has been said to be in 

 general similar to fermentation — that it is effected by the bacteria 

 in seeking their food. If oxygen be abundant, putrefaction occurs; 

 if it be scant or absent, then fermentation takes place, for the tiny 

 organisms require oxygen, and, if the air fails them, they pull to pieces 

 the organic matters near them to obtain it. In doing this they get 

 the nitrogen into such shape that the plants can use it, and thus 

 digest their food for them. All organic matter contains carbon, 

 hydrogen, and oxygen as a general rule, and to these are often united 

 phosphorus, sulphur, nitrogen, and others, making very complex 

 arrangements, veritable houses of cards, in fact, only held together 

 by the strange power of life. When a leaf falls or a bird dies, some 

 of these combinations are broken, and then the bacteria and other 

 lowly organisms have full sway, for living matter is impregnable to 

 all save a few of them. As oxygen or something else is taken out 

 of the complex molecules, the compound falls to pieces, but as in 

 the kaleidoscope the bits of colored glass tumble into endless vari- 

 eties of symmetrical figures, so do the atoms fall into new combina- 

 tions. If the keystone of an arch be removed, the stones fall apart; 

 but atoms, unlike bricks or stones, can not stand alone as a rule; 



