Although the hardness and solidity of the osseous texture seem to be
opposed to every kind of extension and contraction, yet these two
phenomena and the properties of texture from which they arise, are
often very evident in it.
The extensibility of the osseous fibres is proved by the observation
of many diseases, for example, the spina-ventosa, the swelling of the
maxillary sinus when it contains a polypus, by the enlargement of
the bones of the cranium in hydrocephalus, &c. I would remark on the
subject of these different distensions, that often by the influence
of analogous causes, the bones which yield and are distended in the
above cases, are broken, worn and destroyed in others. A polypus of
the nose breaks through the naso-palatine partition, without having
first distended it; aneurism of the aorta does not bend the sternum
or the vertebræ, but it breaks through and destroys these bones.
Whence arises this difference from causes nearly the same? This is not
easily determined. The contractility of texture is very evident in the
bones, when the cause which distended the fibres is removed. We see
the alveoli contract, and become effaced, when a tooth has been drawn
from them. The diminution of the thickness of the jaw after cutting
the teeth arises only from the contraction of its fibres, which are
no longer distended as much, because the root is not so broad as the
crown, which had till then been wholly in the bone. The maxillary sinus
contracts when a fungus is removed from it, or pus is discharged from
the carious bone, &c. If death was not too soon the consequence of the
puncture of the head of hydrocephalic patients, I am persuaded that we
should see the bones gradually contract, and restore the cavity of the
cranium to its natural dimensions. When we remove the dead piece from
a long bone in necrosis, the new bone, formed on the exterior by means
of the periosteum contracts in an evident manner. In paralysis of the
optic nerve, its foramen becomes narrower. The orbit contracts when a
cancerous eye has been extirpated. I have dissected the carotid canal
in a dog whose carotid I had tied; there was no contraction because the
blood coming by anastomoses dilated the artery to the usual size.
This contraction of the bones, by means of the contractility of
texture, is not so sudden as that of the muscles, the skin, &c. when
they are no longer distended by a tumour, an aqueous collection, &c.
This arises from the difference of the organic texture, from the
rigidity of osseous fibres owing to the calcareous substance they
contain, &c. Thus the organic sensibility is less evident in them.