Everybody has seen a common fowl.  It is an active creature which runs about and sometimes flies.  It has a body covered with feathers, provided with two wings and two legs, and ending at one end in a neck terminated by a head with a beak, between the two parts of which the mouth is placed.  The hen lays eggs, each of which is inclosed in a hard shell.  If you break an egg the contents flow out and are seen to consist of the colorless glairy “white” and the yellow “yolk.”  If the white is collected by itself in water and then heated it becomes turbid, forming a white solid, very similar to the vegetable albumin, which is called animal albumin.

If the yolk is beaten up with water, no starch nor cellulose is obtained from it, but there will be plenty of fatty and some saccharine matter, besides substances more or less similar to albumin and gluten.

The feathers of the fowl are chiefly composed of horn; if they are stripped off and the body is boiled for a long time, the water will be found to contain a quantity of gelatin, which sets into a jelly as it cools; and the body will fall to pieces, the bones and the flesh separating from one another.  The bones consist almost entirely of a substance which yields gelatin when it is boiled in water, impregnated with a large quantity of salts of lime, just as the wood of the wheat stem is impregnated with silica.  The flesh, on the other hand, will contain albumin, and some other substances which are very similar to albumin, termed fibrin and syntonin.

In the living bird, all these bodies are united with a great quantity of water, or dissolved, or suspended in water; and it must be remembered that there are sundry other constituents of the fowl’s body and of the egg, which are left unmentioned, as of no present importance.

The wheat plant contains neither horn, nor gelatin, and the fowl contains neither starch, nor cellulose; but the albumin of the plant is very similar to that of the animal, and the fibrin and syntonin of the animal are bodies closely allied to both albumin and gluten.

That there is a close likeness between all these bodies is obvious from the fact that when any of them is strongly heated, or allowed to putrefy, it gives off the same sort of disagreeable smell; and careful chemical analysis has shown that they are, in fact, all composed of the elements carbon, hydrogen, oxygen, and nitrogen, combined in very nearly the same proportions.  Indeed, charcoal, which is impure carbon, might be obtained by strongly heating either a handful of corn, or a piece of fowl’s flesh, in a vessel from which the air is excluded so as to keep the corn or the flesh from burning.  And if the vessel were a still, so that the products of this destructive distillation, as it is called, could be condensed and collected, we should find water and ammonia, in some shape or other, in the receiver.  Now ammonia is a compound of the elementary bodies, nitrogen and hydrogen; therefore both nitrogen and hydrogen must have been contained in the bodies from which it is derived.