DISTINCTION BETWEEN ANIMALS AND PLANTS. 7 



to be classed as belonfjina: to eitber one brancb or the 

 otber, but bound to take a direction of their own. 



From a strictly scientific point of view the crucial 

 distinction between animals and plants lies in their 

 chemical relationships, regarding which a few words of 

 explanation; must here be given. The food of plants 

 . consists of carbonic acid gas (carbonic anhydride, 

 CO2), water, and mineral salts ;i the first is taken in 

 by the pores of the. leaves, the third (along with the 



• water in which they are dissolved in the soil) by the 

 fibrils of the roots. The mineral salts include com- 

 pounds of nitrogen, which element is more or less 

 entirely supplied to plants by derivatives from the 

 ammonia and other nitrogen compounds contained in 

 the decomposing sewage products of the animal king- 

 dom. The food of animals, on the contrary, consists 

 of water and organic compounds ; and the animal body 



- has no power to assimilate mineral matter, except in 

 the case of its occasional artificial admixture with 

 organic substances, as in the use of table salt or mineral 

 medicines, or of its natural admixture in the fresh 

 juices of plants and animals. These present a quantity 

 of certain mineral matters, but in a state of mixture 

 or perhaps sometimes of combination with the organic 



• compounds, that especially favours their assimilation. 



One of the differences between the organic com- 

 pounds and mineral salts is, that in the former the 



' The reader who is unacquainted with the terms used in 

 Chemistry should refer to an elementary text-book dealing 

 ' with this subject. 



