Authors speak of a delicate membrane that lines the interior of all
the osseous cells, and which they consider to be the exhalant organ of
the medullary fluid. I have never been able, though my researches have
been numerous, to discover a similar membrane. We see only the vascular
elongations of which I have spoken, which, greatly multiplied, appear
in fact to form a membrane, but when examined attentively are found to
be very distinct from each other, not continuous, except at the place
of the anastomoses, and leaving between them many small spaces in which
the bone is not covered, but is in contact with the medullary fluid.
The exhalation then of this fluid appears to arise only from this
vascular net-work, and in this respect it is analogous to that of the
compact substance, which evidently contains no membrane, and the pores
of which are however found filled with this medullary fluid, as is
proved by the combustion of the compact texture and its exposure to the
sun or artificial heat.