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Of all the characteristic functions of life nutrition is certainly 
the most important. It is by means of it and with the assistance of 
-certain inanimate products which we call food that man in the first 
stages of his existence succeeds in increasing his size to a mit which 
depends upon his nature and later on succeeds in constantly repair- 
ing the loss of material which he suffers in his contact with the out- 
side world. 
’ Nutrition has everywhere the same object, but it may be accom- 
plished in two entirely different ways. In the animal, considered 
as essentially a producer of power, nutrition is nothing more than 
a transformation of forces similar to that which we realize arti- 
ficially in our steam engines. Nourishment must therefore contain 
within itself the motive power to be used by the organism which 
absorbs it. In other words, it should be so composed as to be capa- 
ble of furnishing heat by transforming itself into more simple ele- 
ments. I speak here of the organic matter which forms, indeed, the 
basis of nourishment in the entire animal kingdom. 
With the plant, on the contrary, which is constantly absorbing 
energy instead of producing it, the nutriment is no longer subject 
to any condifions, and thanks to the living force of the solar rays, 
which the plant stores up in its chlorophyllian tissues, it succeeds in 
nourishing itself on true products of combustion—such as water, 
carbonic acid, and nitric acid. In other words, on substances which 
have reached their maximum stability and which by a concentration 
of force it converts to the condition of organic matter. 
It is thus that the vegetable kingdom has acquired that wonderful 
power of combination which the methods of our laboratories so 
rarely attain. It is thus above all that it is able to continually re- 
produce the combustible matter which the animal kingdom has con- 
sumed, and that it enables a limited quantity of matter to suffice for 
the support of an indefinite number of generations belonging by 
turns to the two kingdoms. . 
By its synthetical nature vegetable nutrition must necessarily pre- 
cede animal nutrition. It is as indispensable to this latter as the 
light of the sun is absolutely necessary to the development of plants; 
and this is not, as we may well believe, the least interesting aspect 
of its study, for it is probable that when we become well acquainted 
with every detail of the changes which contribute to the organization 
of mineral matter in the vegetable tissues we shall then be able, by 
making use of suitable agricultural methods, to. assist the nutrition 
of plants artificially and at the same time to improve our own food, 
which is the object of all progress in agriculture. 
We must also in this connection call attention to the present almost 
universal use of chemical fertilizers. This is certainly not the only 
improvement which we have a right to expect from scientific re- 
searches, and we shall now see that recent researches relating to the 
assimilation of liberated nitrates by plants are of a nature to make us 
look for others and perhaps equally important steps of progress. 
Analysis shows that besides some mineral substances whose role is 
still very obscure, the cellular juice of all vegetables is formed of 
carbon and nitrogen combined with the elements of water—that is to 
say, with hydrogen and oxygen. These latter are evidently provided 
by the water which impregnates the earth, and as there is almost 
aves a sufficient quantity of this, we need not occupy ourselves with 
it here. 
