Zoonomia, Vol. I | Page 4

the
prosecution of the work, the reader is troubled with them in this place,
and is intreated to keep them in his mind as he proceeds, and to take
them for granted, till an apt opportunity occurs to evince their truth; to

which I shall premise a very short outline of the animal economy.
* * * * *
I.--1. The nervous system has its origin from the brain, and is
distributed to every part of the body. Those nerves, which serve the
senses, principally arise from that part of the brain, which is lodged in
the head; and those, which serve the purposes of muscular motion,
principally arise from that part of the brain, which is lodged in the neck
and back, and which is erroneously called the spinal marrow. The
ultimate fibrils of these nerves terminate in the immediate organs of
sense and muscular fibres, and if a ligature be put on any part of their
passage from the head or spine, all motion and perception cease in the
parts beneath the ligature.
2. The longitudinal muscular fibres compose the locomotive muscles,
whose contractions move the bones of the limbs and trunk, to which
their extremities are attached. The annular or spiral muscular fibres
compose the vascular muscles, which constitute the intestinal canal, the
arteries, veins, glands, and absorbent vessels.
3. The immediate organs of sense, as the retina of the eye, probably
consist of moving fibrils, with a power of contraction similar to that of
the larger muscles above described.
4. The cellular membrane consists of cells, which resemble those of a
sponge, communicating with each other, and connecting together all
the other parts of the body.
5. The arterial system consists of the aortal and the pulmonary artery,
which are attended through their whole course with their correspondent
veins. The pulmonary artery receives the blood from the right chamber
of the heart, and carries it to the minute extensive ramifications of the
lungs, where it is exposed to the action of the air on a surface equal to
that of the whole external skin, through the thin moist coats of those
vessels, which are spread on the air-cells, which constitute the minute
terminal ramifications of the wind-pipe. Here the blood changes its
colour from a dark red to a bright scarlet. It is then collected by the

branches of the pulmonary vein, and conveyed to the left chamber of
the heart.
6. The aorta is another large artery, which receives the blood from the
left chamber of the heart, after it has been thus aerated in the lungs, and
conveys it by ascending and descending branches to every other part of
the system; the extremities of this artery terminate either in glands, as
the salivary glands, lacrymal glands, &c. or in capillary vessels, which
are probably less involuted glands; in these some fluid, as saliva, tears,
perspiration, are separated from the blood; and the remainder of the
blood is absorbed or drank up by branches of veins correspondent to
the branches of the artery; which are furnished with valves to prevent
its return; and is thus carried back, after having again changed its
colour to a dark red, to the right chamber of the heart. The circulation
of the blood in the liver differs from this general system; for the veins
which drink up the refluent blood from those arteries, which are spread
on the bowels and mesentery, unite into a trunk in the liver, and form a
kind of artery, which is branched into the whole substance of the liver,
and is called the vena portarum; and from which the bile is separated by
the numerous hepatic glands, which constitute that viscus.
7. The glands may be divided into three systems, the convoluted glands,
such as those above described, which separate bile, tears, saliva, &c.
Secondly, the glands without convolution, as the capillary vessels,
which unite the terminations of the arteries and veins; and separate both
the mucus, which lubricates the cellular membrane, and the perspirable
matter, which preserves the skin moist and flexible. And thirdly, the
whole absorbent system, consisting of the lacteals, which open their
mouths into the stomach and intestines, and of the lymphatics, which
open their mouths on the external surface of the body, and on the
internal linings of all the cells of the cellular membrane, and other
cavities of the body.
These lacteal and lymphatic vessels are furnished with numerous valves
to prevent the return of the fluids, which they absorb, and terminate in
glands, called lymphatic glands, and may hence be considered as long
necks or mouths belonging to these glands. To these they convey the

chyle and mucus, with a part of the perspirable matter, and atmospheric
moisture; all which, after having passed through these glands, and
having suffered some