dy fibre.
All are composed of the same few, simple elements, arranged in
different order and proportions."

422. "In like manner we find the vessels, in animated bodies, capable
of forming all the various textures and substances which compose the
frame; the cellular tissue, the membranes, the ligaments, the
cartilages, the bones, the marrow, the muscles with their tendons, the
lubricating fluid of the joints, the pulp of the brain, the
transparent jelly of the eye; in short, all the textures of the
various organs of which the body is composed, consist of similar
ultimate elements, and are manufactured from the blood."

423. Of the agents that produce or direct the different secretions, we
have no very accurate knowledge. Some have supposed this function to
be mechanical, others a chemical process, but experiments prove that
it is dependent on nervous influence. If the nerves are divided which
are distributed to any organ, the process of secretion is suspended.
It is no uncommon occurrence, that the nature of milk will be so
changed from the influence of anger in the mother, as to cause
vomiting, colic, and even convulsions, in the infant that swallows it.
Unexpected intelligence either of a pleasant or unpleasant character,
by its influence on the nervous system, will frequently destroy the
appetite. Sometimes mental agitation, as fear, will cause a cold sweat
to pervade the surface of the body.

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421. What is said respecting secreted substances? Do vegetables
possess the property of secretion? 422. From what are the various
textures formed? 423. Have we accurate knowledge of the agents that
produce secretion?

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424. Secretions are constantly maintained, during life, from the
serous membrane, by the action of the internal exhalants. The fluid
which is exhaled bears some resemblance to the serum of the blood. Its
use is to furnish the organs, which are surrounded by this membrane,
with a proper degree of moisture, and thus enables them to move easily
on each other, as those within the chest and abdomen.

425. The cellular tissue exhales a serous fluid, and when it becomes
excessive in quantity, general dropsy is produced. Fat is another
secretion, which is thrown out, in a fluid state, from the cellular
membrane. It is deposited in little cells, and exists in the greatest
abundance between the skin and the muscles. Its use seems to be, to
form a cushion arou