SPONTANEOUS GENERATION 59 



all parts of the earth. The forms of plant food 

 which the plant commonly uses, are carbon dioxide, 

 represented by the formula C O2 ; water, the formula 

 of which is H2 O, and ammonia, with the formula- 

 N H3, and a nitrate, with the formula K N O3. 



The plant obtains its carbon from carbon dioxide, 

 which it takes from the air; its hydrogen and oxygen 

 mostly from water, which it obtains from the soil, and 

 its nitrogen from some compound of ammonia or 

 some nitrate, both of which it gets in solution in 

 water from the soil. 



It will be noticed that the formulas of these plant 

 foods are simple; that is, the molecule of each kind 

 has but few atoms, as shown by the formula. The 

 plant alone, and not the animal, has the power to take 

 these comparatively simple inorganic compounds and, 

 by the aid of heat, light and the other usual physical 

 conditions, convert them into the exceedingly com- 

 plex tissues that compose its body. The most essen- 

 tial of these tissues, the one that is necessarily pres- 

 ent in every organic being, is protoplasm. This is the 

 substance in which life manifests itself especially. It 

 is composed of the four elements named above, and 

 it is exceedingly complex in its structure, each mole- 

 cule of protoplasm containing hundreds of atoms. 

 One of the formulas given for protoplasm is C72 Hm 

 NisSOk. 



In order to prove that spontaneous generation has 

 taken place, it would be necessary to show that a 

 living being, composed of the exceedingly complex 

 substance, protoplasm, capable of propagating its 

 kind by the ordinary method of generation, can be 

 produced from the above four elements and their 

 compounds, by the action of the forces of nature. It 

 will be noticed that this is not simply a question of 

 chemical composition, but also of life and of ability 



