CHAPTER IV 

 ANIMALS AND THEIR PRODUCTS. 



CONNECTION BETWEEN SOILS, PLANTS, AND 

 ANIMALS. 



179. In a former part of this work were described 

 about 20 substances, all of which, either as permanent 

 ingredients of the soil, or less permanently connected 

 with it, contribute to the growth of plants. It may 

 now be stated that the permanent ingredients of soils 

 are fewer in number. Soils are substantially made up 

 of organic matter, potash^ soda^ lime, magnesia, oxides of 

 iron, oxide of mayiganese, sulphuric acid, phosphoric acid^ 

 carhonic acid, chlorine, silica and alumina, 



180. These twelve constitute soils. If we omit the 

 last, the remaining eleven constitute plants ; and if we 

 strike off the last two, the remaining ten constitute 

 animals. Alumina stops in the soil ; silica, e±cept in 

 exceedingly minute quantities, stops with the plant ; 

 the other ten pass from the soil into the plant ; then 

 from the plant into the animal ; and finally back into 

 the soil. From this it will be seen that when we ex- 



