Though we know not what is the structure of the exhalants, yet we
cannot doubt but that this structure differs remarkably in the
different systems. Observe in fact that these vessels enter, as
it were, like elements into the textures they compose, and that
consequently they must necessarily partake of the different and
distinctive characters which these textures exhibit.
It is to this difference that we must refer without doubt what we see
in injections. They go out, if they are fine, by the mucous, serous and
even cellular exhalants; but those which furnish the synovia, transmit
them with much more difficulty; it is the same in the capillary system;
whilst the serous surfaces in this system are filled with great ease,
and blackened by injections, as it were at will, the synovial surfaces
are penetrated with much more difficulty.