FOOD CYCLES AND MICEOBES 127 



day as the daily bread for the Vegetable Kingdom. 

 True it is that here, again, in this great change 

 only chemical and physical forces are employed. 

 Microbes lend no aid. Leaves of the plants, en- \ 

 gineered by sun power, break up the molecules of 

 the 14,200,000 tons of carbon, and let the 7,000,000 

 tons of oxygen go free back into the air whence it 

 came. 



But what of it? What if microbes have nothing 

 to do with these chemical and physical changes? 

 It is yet true that, all the while, these changes are 

 taking place, microbes are doing a more basic work. 

 Their work in the grand, order of this oxygen cycle 

 is first. All the work done by the chemical and 

 physical forces rests upon this previous work done 

 by microbes as on a foundation stone. In each of 

 the three chemical fires in the breathing organs 

 of animals, in the furnace where coal or wood is 

 burned, or in dead bodies, the carbon in each 

 case which makes the fire possible, is vegetable in 

 its origin. But the growth, and the very existence 

 of the vegetable, in each case, is made possible 

 only by the fixation of nitrogenous food in the soil 

 by microbes. 



This cycle of oxygen, therefore, like the other 

 food cycles, is made complete and permanent, and 

 the order of life on the earth maintained, only by 

 the helping hand of our Invisible Friends. 



