he circulation; and those, which give something to it.
Those, which take their fluid from the circulation are the various glands,
by which the tears, bile, urine, perspiration, and many other secretions
are produced; these glands probably consist of a mouth to select, a belly
to digest, and an excretory aperture to emit their appropriated fluids; the
blood is conveyed by the power of the heart and arteries to the mouths of
these glands, it is there taken up by the living power of the gland, and
carried forwards to its belly, and excretory aperture, where a part is
separated, and the remainder absorbed by the veins for further purposes.

Some of these glands are furnished with long convoluted necks or tubes, as
the seminal ones, which are curiously seen when injected with quicksilver.
Others seem to consist of shorter tubes, as that great congeries of glands,
which constitute the liver, and those of the kidneys. Some have their
excretory apertures opening into reservoirs, as the urinary and
gall-bladders. And others on the external body, as those which secrete the
tears, and perspirable matter.

Another great system of glands, which have very short necks, are the
capillary vessels; by which the insensible perspiration is secreted on the
skin; and the mucus of various consistences, which lubricates the
interstices of the cellular membrane, of the muscular fibres, and of all
the larger cavities of the body. From the want of a long convolution of
vessels some have doubted, whether these capillaries should be considered
as glands, and have been led to conclude, that the perspirable matter
rather exuded than was secreted. But the fluid of perspiration is not
simple water, though that part of it, which exhales into the air may be
such; for there is another part of it, which in a state of health is
absorbed again; but which, when the absorbents are diseased, remains on the
surface of the skin, in the form of scurf, or indurated mucus. Another
thing, which shews their similitude to other glands, is their sensibility
to certain affections of the mind; as is seen in the deeper colour of the
skin in the blush of shame, or the greater paleness of it from fear.

III. Another series of glandular vessels is called the absorbent system;
these open their mouths into all the cavities, and upon all those surfaces
of the body, where the excretory apertures of the other glands pour out
their fluids. The mouths of the absorbent system drink u