PLANTS AND ANIMALS DISTINGUISHED. 
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pendent for their food on the compounds put together in 
plants. Colorless plants, possessing no chlorophyl, feed, 
like animals, on organic compounds. No living being is 
able to combine the simple elements—carbon, oxygen, hy¬ 
drogen, and nitrogen—into organic compounds. 
The food of plants is gaseous (carbon dioxide and am¬ 
monia) or liquid (water), that of animals usually more or 
less solid. The plant, then, absorbs these foods through 
its outer surface, while the animal takes its nourishment 
in larger or smaller masses, and digests it in a special cav¬ 
ity. A few’ exceptions, however, occur on both sides. 
Certain moulds seem to swallow their food, and certain 
animals, as the tape-worm, have no digestive tract. 
Plants are ordinarily fixed, their food is brought to 
them, and a large share of their work, the formation of 
organic compounds, is done by the force of the sunlight; 
w T hile animals are usually locomotive, must seek their 
food, and are unable to utilize the general forces of nature 
as the plant does. The plant is thus able to grow much 
more than the animal, as very little of the nourishment 
received is used to repair waste, while in most animals the 
time soon comes when waste and repair are approximately 
equal. But in both all work done is paid for by waste of 
substance already formed. 
In combining carbon dioxide and water to form starch 
the plant sets oxygen free (6(C0 2 ) + 5(H 2 0) = C 6 H 10 O 5 + 
6(0 2 )): in oxidizing starch or other food the animal uses 
oxygen and sets carbon dioxide free. The green plant in 
the sunlight, then, gives off oxygen and uses carbon diox¬ 
ide, while plants which have no chlorophyl, at all times, 
and all plants in the darkness, use oxygen and give off 
carbon dioxide, like an animal. Every plant begins life 
like an animal—a consumer, not a producer: not till the 
young shoot rises above the soil, and unfolds itself to the 
light of the sun, at the touch of whose mystic rays chlo- 
