NUTRITIVE PRINCIPLES OF PLANTS. 261 
fibres of the root, the same wonderful properties; the plant is 
alive, as truly as any part of the body of the living animal; they 
both receive, on the same principle, the properties of growth, re- 
production, and the power of replacing again in the system what 
has been consumed. Of these properties true vegetable life con- 
sists; it is developed without consciousness. 
Chemically speaking, animal life, although of a rank infinitely 
higher, generates only the substance of the nerves and of the 
brain, which are altogether wanting in plants. Although animals 
receive from vegetables all the ingredients requisite for the for- 
mation of blood, and cannot by their own organization gene- 
rate them from carbonic acid and. ammonia, as plants do, the 
power belongs to them alone of producing those bodies of a 
higher order, such as in the complex constituents of the brain, 
the spinal marrow and the nerves. Animals must have peculiar 
organs for the exercise of the will, the feelings, and locomotion ; 
and these organs must be produced from that part to which the 
impulse is given. Physiology gives us no decided information 
on these points; the spleen and the numerous glands must all 
have some part to perform in the body, and a necessary one too, 
or they certainly would not exist. 
The growth of plants depends on the continual supply of car- 
bon, and two other elements; and this supply is obtained by 
the separation of oxygen from the ingredients of their food. 
The growth of the organs of a graminivorous animal must 
depend also on a similar separation of oxygen; but we know 
that the life of animals, on the contrary, is characterized by a 
constant absorption of oxygen, although it does not remain in 
the body; and it is known, from a number of simple facts, that 
besides the oxygen of the atmosphere, which escapes in combi- 
nation with carbon, another portion arising from the food must 
escape also, under certain circumstances, as carbonie acid. 
This last oxygen arises from that nutriment which contains no 
nitrogen, when fat is formed; starch, sugar, and gum, cannot 
be used by animals for the formation of blood, or muscular fibre, 
because the azotized nourishment they receive contains all that 
is wanted. The membranes, the cellular tissue, skin, horn, and 
the claws of animals, contain more nitrogen, in proportion to 
their carbon, than albumen and fibrin. These latter must give 
up a certain portion of their carbon if the former are produced 
from the blood: that they are produced from substances with no 
nitrogen, is impossible. | 
