COMPARISON BETWEEN ANIMALS AND PLANTS. 2J5 
t(;rs of organization; that it seems impossible to distinguish them by 
any trait that belongs exclusively to either; that the connexion be- 
tween them appears the most striking in the least perfect species of 
both kingdoms; and that as we recede from this point, the differ- 
ences become more numerous and more marked. 
We may illustrate this view, by imagining two_ascending chains, 
rising from one common point, each side of the chain becoming 
more and more unlike in proportion to the intervening distance 
from the centre. From this same central point, also proceeds the 
chain of inorganized substances ; some imperfect animals resem- 
bling plants in their outward form, some, both of animals and plants, 
resembling minerals in their hard and calcareous coverings and 
shapeless forms. 
Having thus learned the almost imperceptible gradations by which 
the animal and vegetable kingdoms are blended, we must, in stating 
the important differences which exist between animals and plants, 
consider the imperfect species of both kinds as exceptions to any- 
general rule, and confine ourselves to perfect animals and plants. 
1st. Plants differ from animals with respect to the elem.ents which 
compose them; carbon^ hydrogen^ and oxygen^ form the base of vege- 
table substances ; animals exhibit the same elements, with this impor 
tant distinction, that carbon prevails in plants, and nitrogen in ani- 
mal food. 
2d. They differ in their food ; plants are nourished with inorgan- 
ized matter, absorbed with water, which holds in solution various sub- 
stances; animals are mostly nourished either by vegetable or other 
animals. 
3d. Plants throw off oxygen gas, and inhale carbonic acid ; ani- 
mals, in respiration, inhale oxygen gas and throw off carbonic acid. 
4th. Although plants and animals both possess a principle of life, it 
is in the one case much more limited than in the other; exhibiting itself 
in plants by a feeble power of contraction or irritability ; in animals 
appearing in sensation, muscular m.ovem,ent, and voluntary motion. 
We see, then, many important differences between perfect animals 
and perfect plants. We have, in numerous instances, pointed out 
striking analogies between the two great divisions of organized bod- 
res : this subject might be greatly enlarged ; but we have already, 
amid the multitude of interesting facts and reflections presented by 
the vegetable creation, far exceeded the bounds originally prescribed. 
A few remarks on the inorganic matter upon and around the earth, 
and our course of Lectures is closed. 
Inorganic bodies form the solid base of the globe. Minerals are 
spread upon the face of the earth, or he buried beneath its surface. 
They form vast masses of rocks, chains of mountains, and the 
ground upon which we tread. The Water occupies a still greater 
surface of the earth than the land ; it is filled with life and animation ; 
the treasures and wonders of the deep seem almost unbounded. 
The Air, lighter than earth and water, extending on all sides about 
forty miles in height, surrounds the whole globe, separating us from 
the unknown elements which exist beyond it. Heat, or Caloric, is a 
subtle fluid which pervades all matter, in an increasing proportion 
from solids to fluids, and fluids to gases. Light, reflecting its hues 
from terrestrial objects, produces, by the decomposition of its rays 
all the beautiful variety of colouring. 
Result of the comparison between animals and vegetables— Chains of bem^s 
proceeding from one point — Differences between animals and plants — Different kin^ia 
df inorganic matter — The Deity manifested in his works. 
2J* 
