The short bones are placed in general in parts where are found united
mobility and solidity, as in the vertebral column, the tarsus, and the
metatarsus. Always small, they are in great number in the regions which
they occupy; their number compensates for their size in the formation
of the parts of the skeleton to which they contribute. It is this
number also, that gives to these parts the union of the two almost
opposite attributes of which we have spoken, viz. solidity, because
the external efforts are lost in the numerous bands which unite them,
and mobility, because the whole of their individual motions gives a
considerable general motion.
There is nothing constant or uniform in the external conformation
of these bones; it is modified according to the general plan of the
whole, of which they are the parts; thus the different uses of the
carpus, metacarpus and vertebral column determine the different forms
of their respective bones. These bones have always many cavities and
eminences upon their external surfaces, necessary for their numerous
articulations, for the insertion of the many ligamentary cords that
unite them, and the muscles that move them.
In the interior, these bones have nothing peculiar, except an abundance
of the texture of the cells which forms them almost wholly, and exposes
them to frequent caries.
Nature is not however regular in the division of bones into long,
flat and short. Here as elsewhere, she disregards our methodical
descriptions, and shows us the bones sometimes exhibiting the character
of long ones and short, and sometimes uniting the attributes of both
these last with the flat ones. The basilary apophysis and the superior
part of the occiput, the body and the lateral portions of the sphenoid,
when placed in contrast, prove this assertion. A bone sometimes by
its external form belongs to the long ones, but from its internal
organization should be classed with the flat, of this the ribs are an
example, &c.