The exhalants are developed preternaturally in many parts; it is
especially in the cysts that this development is best seen. Their
internal surface, ordinarily smooth, pours out very different fluids,
according to the particular sensibility they possess. When we open
these cysts, the exhalants furnish new fluids, and it is often
necessary to remove them to prevent exhalation. Sometimes instead of
the fluid that is ordinarily exhaled there, the blood is thrown out, as
happens on the serous surfaces; for example, I have found very bloody
serum in the encysted dropsies of the ovarium; latterly I have seen
in them coagulated blood. I would observe that this is an essential
difference to be added to those mentioned above, between the fluids
that are exhaled and those that are secreted. These last are never
preternaturally poured out in a cyst. We never find preternaturally
a quantity of bile, of urine, saliva, serum, &c. whilst we often
find serum, as in encysted dropsies, fat as in steatoma and other
tumours which have a fatty liquid analogous to this fluid, synovia,
as in the tumours called ganglions, when they are not dilatations of
the synovial glands, which have cysts preternaturally produced, &c.
Whence arises this difference? it would be necessary that the glands
should be preternaturally developed in our parts, in order that the
secreted fluids might be preternaturally separated from the blood, now
the structure of these organs is too complicated, their organization
supposes too many conditions, to admit of their preternatural
development. On the contrary, the simple organization of the exhalant
surfaces, which have only vessels continuous with the arteries, and
without an intermediate organ, requires much less for them to grow
preternaturally in parts, in which they were before unknown.
Sometimes the fluids exhaled preternaturally do not collect in a cyst;
they continually flow out; this is what takes place in fistulas, and
other preternatural or artificial drains that are made in our organs.
Then the cellular texture, constantly preserving the preternatural
modification of sensibility that it has taken locally from a deposit,
or any other circumstance, constantly continues to pour out a fluid
different from the serum that is exhaled in a natural state.