A Book of Natural History | Page 4

will collect at the bottom of the vessel. This substance is called
vegetable albumin.
Besides the albumin, the gluten, and the starch, other substances about
which this rough method of analysis gives us no information, are
contained in the wheat grain. For example, there is woody matter or
cellulose, and a certain quantity of sugar and fat. It would be possible

to obtain a substance similar to albumin, starch, saccharine, and fatty
matters, and cellulose, by treating the stem, leaves, and root in a similar
fashion, but the cellulose would be in far larger proportion. Straw, in
fact, which consists of the dry stem and leaves of the wheat plant, is
almost wholly made up of cellulose. Besides this, however, it contains
a certain proportion of mineral bodies, among them, pure flint or silica;
and, if you should ever see a wheat rick burnt, you will find more or
less of this silica, in a glassy condition, in the embers. In the living
plant, all these bodies are combined with a large proportion of water, or
are dissolved, or suspended in that fluid. The relative quantity of water
is much greater in the stem and leaves than in the seed.
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.
It is certain, then, that very similar nitrogenous compounds form a very
large part of the bodies of both the wheat plant and the fowl, and these
bodies are called proteids.
It is a very remarkable fact that not only are such substances as albumin,
gluten, fibrin, and syntonin, known exclusively as products