| moticed in the article ArcvonNTUum.
| and less as we descend in the scale.
| sions from without are received immediately by the
| organs of sense, which become more numerous and
| hunger of winter.
| serpents and crocodiles, which lie buried in the dry
| mud during the summer droughts of the tropics.
| be mentioned, the faculty of giving light (glowworm,
| which they are composed ; second, to investigate the
ANIMAL AND ANIMAL KINGDOM—ANIMAL CHEMISTRY.
| limits; often to one circumscribed range of climate,
| one species of food, one medium. To go beyond
| from which even man with all his powers of adapta-
| of mind : in those high in the scale, this mental life
Light also is essential to many, though most of the
colourless animals of the lower classes can dispense
with it. With regard to outward pressure, the
limits are wide, as is seen in the condor soaring to a
height of 20,000 feet, and the whale descending to a
depth of 1000 feet below the surface of the sea. But
individual animals are confined to much narrower
those limits, though it does not always occasion
death, yet gives rise to various degrees of degeneracy,
tion is not exempt.
Most animals give more or less strong indications
rises to intellect capable of cultivation, while, in the
lower classes, it appears as instinet confined to a few
operations. For communicating with the outer world,
vertebrated animals are provided with a mnervous
system in connection with a central brain—a cerebral
nervous system ; the ganmglionic nervous system of
the lower animals seems to serve this purpose less
The impres-
complex the higher the animal stands in the scale;
among the highest, five senses are usually distin-
guished, which are variously developed in different
species—in none so harmoniously as in man.
Nocturnal sleep, being the means of gathering
strength for the activity of the waking hours, stands
in intimate relation to that activity, and therefore
is wanting in beings low in the scale. Winter sleep,
or hybernation (q.v.), serves many animals instead of
migration, to enable them to outlive the cold and
Analogous is the summer sleep of
Of the other vital manifestations of animals may
meduse), and that of developing electricity, both
possessed only by a few ; also voice, belonging almost
exclusively to vertebrate animals, and of them chiefly
to the warm-blooded.
A very remarkable peculiarity occurs in some of
the lowest kinds of animals, in what may be termed
a composite life ; individuals which separately mani-
fest many of the powers of life, being united in part
of their frame, many of them together into one living
mass. Of this, examples are numerous among the
Zoophytes (q. v.), some of which have already been
Apart from the transforming and modifying influ-
ence of man, the animals and plants of a district—
its fauna and flora—give it life and character. To
man himself, animals stand in a variety of relations
of the highest importance. Some are directly useful
to him for labour, food, the chase, &c. ; others hurt-
ful, as destroyers of vegetation, as beasts of prey, as
vermin, or by their poisons.—The number of known
species of animals amounts at present to about
130,000. To describe and classify these on scientific
principles, is the object of Zoology (q. v.).
ANIMAL CHEMISTRY. The object of re-
searches into the chemical nature of animal sub-
stances is twofold : First, to classify the proximate
or immediate component ingredients of the animal
body, study their properties, their mutual relations
and metamorphoses, and the ultimate elements of
processes that go on during the elaboration and
assimilation of new materials, and the wearing out
and excretion of old—processes that, taken together,
constitute nutrition, or the vegetative side of animal
life. Without a pretty complete knowledge of the
the second ; and it is chiefly owing to the great pro-
gress that has been made within the last thirty years
in the knowledge of the chemical properties of the
animal compounds containing nitrogen, that we owe
the recent advance in our knowledge of the chemical
processes of life. That advance is not the less decided
that we are still far from a complete understanding
of them. The general laws of chemistry are now
traced into the province of organic nature much
further than formerly, and the abrupt partition
between the two is removed. It is still acknowledged
that these laws operate differently within the sphere
of organic life, from what they do without; but
instead of resting contented with saying, that owing
to the vital force this could not be otherwise, the
aim is now to trace the why and wherefore of this
modified action as far as possible.
In the animal body, two classes of substances may
be distinguished : those that properly compose the
body, and those that are on the way either into it
or out of it. The former, or actual components of
the body, are, again, of two kinds: 1. Substances
that compose the actual tissues of the organs, and in
which the vital functions seem properly to inhere ;
the substances, namely, of muscle, of nerve, of brain,
of membranes, sinews, and the organic part of the
bones. All these agree in consisting chiefly of
carbon, hydrogen, nitrogen, and oxygen, with usu-
ally minute proportions of sulphur and phosphorus.
But in respect of their mode of composition, they
fall into two classes—those that yield gelatine on
boiling, and those that do not. To the former belong
the substance of the cartilages, bones, sinews, and
skin; to the latter, the fibrin of the muscles and of
the blood corpuscles, the albumen of the nerves
and blood, the caseine of milk, &c. These last are
the so-called compounds of proteine (q.v.). In
the living tissues, all these matters are combined
with about 90 per cent. of water. 2. Besides the
above, which are the real animalised or wvital
substances, the animal body contains substances
which are merely deposited in the cells and inter-
stices of the former for imparting colour, solidity,
elasticity, &c. Of this kind are fat, the earthy
matter of the bones, pigment, &c. Whether the
minute quantities of common salt and of phosphates
that are found in all parts of animals essentially
belong to the constitution of the substance they are
associated with, is not yet made out, but it is
extremely probable they do; at all events, they play
a very important part.
The substances that are on their way into and
out of the body, form on the one hand the contents
of the digestive organs, and on the other those of
the organs of excretion. The vascular system forms
the means of communication between both and the
substance of the body, and the blood is the carrier
of all that enters that substance or leaves it. In
the digestive organs, accordingly, we find, along with
the unaltered materials of the food, the various
products of their digestion, and at last the useless
refuse, not absorbable by the vascular system, and
the various fluids—some acid, some alkaline —added
to the food to effect its digestion, such as the saliva,
gastric juice, and bile.
The matters prepared in the digestive organs for
being taken up into the blood, either enter the
venous system directly, or get there by first going
through the lymphatic system. This last contains a
fluid which is chemically very like the blood, but
colourless—the chyle, namely. This fluid and the
blood contain the so-called proteine compounds
derived from the food, partly in solution, and partly
solid in the blood corpuscles. Arterial blood
contains, besides, all those salts and other substances
first part, no successful researches can be made in
266
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