Though the medullary system is only met with in the bones, and
though its principal uses appear to relate entirely to them, yet its
properties and life differ so much from the properties and life of
these organs, that we are compelled to examine them in a separate
manner.
We distinguish two kinds of medullary systems; one occupies the texture
of the cells of the extremities of the long bones, and the whole of the
interior of the short and flat bones; the other is found only in the
middle part of the first; let us examine each separately.