26 FAMILIAR LETTERS ON CHEMISTRY. 



glutinous property belongs, not to vegetable fibrine, but to a foreign substance, 

 present in small quantity, which is not found in the other cerealia. 



The method by which it is obtained sufficiently proves that it is insoluble in 

 water ; although we cannot doubt that it was originally dissolved in the vegetable 

 juice, from which it afterwards separated, exactly as fibrine does from blood. 



The second nitrogenizod compound remains dissolved in the juice after the 

 separation of the fibrine. It does not separate from the juice at the ordinary 

 temperature, but is instantly coagulated when the liquid containing it is heated to 

 the boiling point. 



When the clarified juice of nutritious vegetables, such as cauliflower, asparagus, 

 mangeiwurzel, or turnips, is made to boil, a coagulum is formed, which it is abso- 

 lutely impossible to distinguish from the substance which separates as a coagulum, 

 when the serum of blood, or the white of an egg, diluted with water, are heated to 

 the boiling point. This is vegetable albumen. It is found in the greatest abundance 

 in certain seeds, in nuts, almonds, and others, in which the starch of the graminese 

 is replaced by oiL 



The third nitrogenized constituent of the vegetable food of animals is vegetable 

 easeine. It is chiefly found in the seeds of peas, beans, lentils, and similar legu- 

 minous seeds. Like vegetable albumen, it is goluble in water, but differs from it 

 in this, that its solution is jnot coagulated by heat. When the solution is heated or 

 evaporated, a skin forms on its surface, and the addition of an acid causes a coagu- 

 lum, just as in animal milk. 



These three nitrogenized compounds, vegetable fibrine, albumen, and easeine, are 

 the true nitrogenized constituents of the food of graminivorous animals ; all other 

 nitrogenized compounds occurring in plants, are either rejected by animals, as in 

 the case of the characteristic principles of poisonous and medicinal plants, or else 

 they occur in the food in such very small proportion, that they cannot possibly con- 

 tribute to the increase of mass in the animal body. 



The chemical analysis of these three substances has led to the very interesting 

 result that they contain the same organic elements, united in the same proportion 

 by weight ; and, what is still more remarkable, that they are identical in composi- 

 tion with the chief constituents of blood, animal fibrine, and albumen. They all 

 three dissolve in concentrated muriatic acid with the same deep purple color, and 

 even in their physical characters, animal fibrine and albumen are in no respect 

 different from vegetable fibrine and albumen. It is especially to be noticed, that 

 hy the phrase, identity of composition, we do not here intend* mere similarity, but 

 that even in regard to the presence and relative amount of sulphur, phosphorus, 

 and phosphate of lime, no difference can be observed. How beautifully and admi- 



Irably simple, with the aid of these discoveries, appears the process of nutrition in 

 animals the formation of their organs, in which vitality chiefly resides ! Those 

 vegetable principles, which in animals are used to form blood, contain the chief 

 constituents of blood, fibrine and albumen, ready formed, as far as regards their 

 composition. All plants, besides, contain a certain quantity of iron, which reap- 

 pears in the coloring matter of the blood. Vegetable fibrine and animal fibrine, 

 vegetable albumen and animal albumen, hardly differ, even in form ; if these prin- 

 ciples be wanting in the food, the nutrition of the animal is arrested ; and when 

 they are present, the graminivorous animal obtains in its food the very same prin- 

 ciples on the presence of which the nutrition of the carnivora entirely depends. 



Vegetables produce in their organism the blood of all animals, for the carnivora, 

 in consuming the blood and flesh of the graminivora, consume, strictly speaking, 

 only the vegetable principles which have served for the nutrition of the latter. 

 Vegetable fibrine and albumen take the same form in the stomach of the gramini- 

 vorous animal as animal fibrine and albumen do in that of the carnivorous animal, 

 j From what has been said, it follows that the development of the animal organism 

 and its growth are dependent on the reception of certain principles identical with 

 -the chief constituents of blood. 



In this sense we may say that the animal organism gives to blood only its form ; 

 that it is incapable of creating blood out of other substances which do not already 

 contain the chief constituents of that fluid. We cannot, indeed, maintain that the 

 animal organism has no power to form other compounds, for we know that it is 

 capable of producing an extensive series of compounds, differing in composition 

 from the chief constituents of blood ; but these last, which form the starting point 

 of the series, it cannot produce. 



The animal organism is a higher kind of vegetable, the development of which 

 begins with those substances with the production of which the life of an ordinary 

 vegetable ends. As soon as the latter has borne seed, it dies, or a period of its life 

 comes to a termination. 



