There are three classes of exhalants which I distinguish by the fluids
or the substances they furnish.
The first class contains those that throw out the fluids not destined
to enter the economy again; such are, 1st, the cutaneous exhalants that
pour out the sweat; 2d, the mucous exhalants that furnish a part of the
pulmonary perspiration, the greatest part being formed, as I shall say,
by the dissolution of the mucous fluids of respiration, which yield
perhaps the gastric, intestinal juices, &c.
In the second class are found the exhalants, that throw out fluids
that remain for some time upon certain surfaces or in certain cells;
and which afterwards taken up by absorption, re-enter the circulation
through the lymphatics. These are, 1st, the serous exhalants which
deposit upon their respective surfaces the serum which lubricates the
membranes and facilitates the motions of the organs they cover; 2d,
the cellular exhalants which pour out into the cells, on the one part
serum, on the other fat; 3d, the medullary exhalants which carry into
the middle of the bones the juices of the same name; 4th, the synovial
exhalants which deposit the synovia, either upon the articulations, or
in the tendinous grooves.
The third class contains the exhalants that carry to all the organs the
nutritive substance that repairs them, and which is afterwards taken up
by absorption, to be replaced by new substances.
I adopt in my course of physiology the division I have just pointed
out, to explain the different exhalations, of which the last evidently
leads me to speak of nutrition, a function which is the general end of
those that form organic life. We can represent in the following table,
all the different exhalations; it presents the assemblage of the organs
that execute them.
┌1st. exterior, ┌1st. Dermoid.
│ open upon │
│ the systems, └2d. Mucous.
│ ┌1st Serous.
│ │2d. Cellular, ┌1st. Serum.
│ │ where they │
EXHALANTS.│ │ pour out, └2d. Fat.
│2d. interior, │ ┌1st. of the short, flat
│ open upon │3d Medullary. │ bones, and the extremities
│ the systems, │ │ of the long ones.
│ │ │2d. of the middle of the
│ │ └ long bones.
│ │
│ │ ┌1st. of the articulations.
│ └4th. Synovial.└2d. of the tendons.
│
└3d. nutritive. Each organized texture has its own
exhalants.
This is an accurate table of all the fluids that go out of the blood,
without the intervention of the glands, and by the way of exhalation.
The two first classes have vessels, as is accurately proved by
experiment, observation and even inspection. As to the nutritive
exhalants, there is no doubt but that new substances are continually
carried to the organs to repair them; now it is necessary that these
substances should have vessels; these vessels certainly cannot draw
what they deposit in them, except from the capillary system in which
they terminate. If injections or other means do not accurately prove
the existence of these exhalants, it seems to me that this reasoning
forces us to admit them.
Physiologists had not hitherto collected together all the exhalations;
each was explained in treating of the system where it was found. I have
thus given reflections upon each in the exposition of the different
textures; the arrangement of the general anatomy required it; but
in works or in lectures on physiology, they ought evidently to be
presented under the same point of view as absorptions.