This system appears to be the expansion of the vessels which penetrate
the bones through the foramina of the second order, that is to say,
through those that go to the common texture of the cells. These
vessels having arrived on the internal surface of the cells, divide
ad infinitum and anastomose in a thousand ways. Their interlacing
gives to the interior of the texture of the cells that red appearance
that characterises it, and which is so much the more evident, as it is
examined at an age nearer infancy, because in fact the vascular system
which is very evident at this period, becomes contracted and effaced as
we recede from it.
These are the vessels which, in the section of the bones of the cranium
by the trephine, give to the saw-dust the redness that is observed.
It is these that produce the same phenomenon in the amputation of the
extremity of the limbs. Though in general they remain loaded with blood
at the moment of death, yet we can, as I have often done, accumulate in
them still more by fine injections, which drive before them that which
is found in the vessels, and concentrate it at their extremities; then
the spongy texture of the adult is almost as red as that of the child
which has not been prepared.