30 FAMILIAR LETTERS ON CHEMISTRY. 



pounds, destitute of nitrogen, which, during the life of the animals, served to 

 support the respiratory process. In such men, confined to an animal diet, it is the 

 carbon of the flesh and of the blood which must take the place of starch and sugar. 



But fifteen pounds of flesh contain no more carbon than four pounds of starch, and 

 while the savage, vrith- one animal and an equal weight of starch, could maintain 

 life and health for a certain number of days, he would be compelled, if confined 

 to flesh alone, in order to procure the carbon necessary for respiration, during the 

 game time, to consume five such animals. 



It is easy to see, from these considerations, how close the connexion is between 

 agriculture and the multiplication of the human species. The cultivation of our 

 crops has ultimately no other object than the production of a maximum of those 

 substances which are adapted for assimilation and respiration, in the smallest pos- 

 sible space. Grain and other nutritious vegetables yield us, not only in starch, 

 sugar, and gum, the carbon which protects our organs from the action of oxygen, 

 and produces in the organism the heat which is essential to life, but also in the form 

 of vegetable fibrine, albumen, and caseine, our blood, from which the other parts of 

 our body are developed. 



Man, when confined to animal food, respires, like the carnivora, at the expense 

 of the matters produced by the metamorphosis of organized tissues ; and, just as 

 the lion, tiger, hyaena in the cages of a menagerie, are compelled to accelerate the 

 waste of the organized tissue by incessant motion, in order to furnish the matter 

 necessary for respiration, so the savage, for the very same object, is forced to 

 make the most laborious exertions, and go through a vast amount of muscular 

 exercise. He is compelled to consume force merely in order to supply matter for 

 respiration. 



Cultivation is the economy of force. Science teaches us the simplest means of 

 obtaining the greatest effect with the smallest expenditure of power, and with given 

 means to produce a maximum of force. The unprofitable exertion of power, the 

 waste of force in agriculture, in other branches of industry, in science, or in social 

 economy, is characteristic of the savage state, or of the want of knowledge. 



In accordance with what I have already stated, you will perceive that the sub- 

 stafiCes, of which tHe^food of man is composed, may be divided into two classes ; 

 in(o ! nitrogenized ancP don-nitrogenized. The former are capable of conversion into 

 blood ; the latter arMncapable of this transformation. 



Out of those substances, which are adapted to the formation of blood, are formed 

 all the organized tissues. The other class of substances, in the normal state of 

 health, serve to support the process of respiration. The former may be called the 

 plastic elements of nutrition; the latter, elements of respiration. 



Among the former we reckon 



Vegetable fibrine. Vegetable Albumen. 



Vegetable casine. Animal flesh. 



Animal blood. 



Among the elements of respiration in our food are 

 Fat. Pectine. 



Starch. Bassorine. 



Gum. Wine. 



Cane Sugar. Beer. 



Grape Sugar. Spirits. 



Sugar of milk. 



The most recent and exact researches have established as a universal fact, to 

 which nothing yet known is opposed, that the nitrogenized constituents of vegetable 

 food have a composition identical with that of the constituents of the blood. 



No nitrogenized compound, the composition of which differs from that of fibrine, 

 albumen, and caseine, is capable of supporting the vital process in animals. 



The animal organism unquestionably possesses the power of forming, from the 

 constituents of its blood, the substance of its membranes and celular tissue, of the 

 nerves and brain, and of the organic part of cartilages and bones. But the blood 

 must be supplied to it ready formed in every thing but its form that is, in its 

 chemical composition. If this be not done, a period is rapidly put to the formation 

 of blood, and consequently to life. 



This consideration enables us easily to explain how it happens that the tissues 

 yielding gelatine or chondrine, as, for example, the gelatine of skin or of bones, 

 are not adapted for the support of the vital process ; for their composition is diffe- 

 rent from that of fibrine or albumen. It is obvious that this means nothing more 

 than that those parts of the animal organism, which form the blood, do not possess 

 the power of effecting a transformation in the arrangement of the elements of gela- 

 tine, or of those tissues which contain it. The gelatinous tissues, the gelatine of the 



