990 The American Naturalist. [December, 
perpetuated by the constant use of the same material over 
and over again. : i 
Now, this is not only true in regard to oxygen and car- 
bonic acid, but it is true also that all the other foods of 
animals and plants are capable of being used over and over 
again. Plants live upon phosphates, sulphates, and nitrates 
chiefly, as well as carbonic acid. Animals live upon such 
things as albuminoids and starches and sugars. Now, plants 
cannot live on the food of animals, and animals cannot live 
on the food of plants. You and I cannot live upon sulphates 
and phosphates and potassium salts and nitrates and carbonic 
acid. These are what we call inorganic compounds in 
nature. Animals cannot feed upon them, but plants can do 
so. The plants can take those materials and manufacture out 
of them the starches and sugars and fats and albuminoids, 
and then we can take the starches and sugars and fats and 
albuminoids which have thus been manufactured for us and 
feed upon them. You see, therefore, that the plants serve as 
a medium of communication between animals and nature. 
The world is made up chiefly of inorganic compounds like 
these phosphates and sulphates and potassium salts, ete., and 
the plants serve as a means of communication between 
animals and the inorganic world, for the plants take these 
inorganic materials and make them into something which we 
can use as food. Plants, then, are the means which we have 
of making use of inorganic nature; or, in other words, the 
whole animal kingdom is parasitic upon plants. But plants 
are in their turn utterly unable to live upon animal foods. A 
plant cannot feed upon albumen, a plant cannot eat starch, & 
plant cannot eat sugar, a plant cannot eat fat; plants are 
unable to use the foods that animals use, and when the body — 
of a plant dies, although it is in a condition to be used as food 
by animals, it is not in a condition to be used again as food 
for plants. The dead body of the bird isin a condition In 
which plants cannot make use of it at all. A plant cannot 4 ; 
use the albumen of the bird’s tissue; a plant cannot use ths 
fats in an animal; a plant cannot feed upon the sugars te 
are in the dead sugar-cane; a plant cannot feed upon u ie 
