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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 increasmg his size to a limit Avhich 

 depends upon his nature and later on succeeds in constantly repair- 

 ing the loss of material Avhich he suft'ers in his contact with the out- 

 side world. 



• Nutrition has everywhere the same object, but it may be accom- 

 plished in two entirely diiferent ways. In the animal, considered 

 as essentially a producer of power, nutrition is nothing more than 

 a transforniation 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 conditions, 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 lalDoratories 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 aninial nutrition. It is as indispensable to this latter as the 

 light of the sun is absolutely necessarj- 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 organizatu)n 

 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 A^egetables is formed of 

 carbon and nitrogen combined w^ith 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 

 always a sufficient quantity of this, we need not occupy ourselves with 

 it here. 



