I. _Texture peculiar to the Organization of the Fibro-Cartilaginous
System._
The texture peculiar to the organization of the fibro-cartilaginous
system is composed, as its name indicates, of a fibrous substance, more
than of a true cartilage.
The fibrous substance is as the base of the organ. We distinguish this
base very plainly in the fibro-cartilages of the tendinous grooves and
of the articulations, in those especially of the body of the vertebræ;
it is much less apparent in the membranous fibro-cartilages. Its
fibres are sometimes interlaced, sometimes parallel. In general its
nature is exactly the same as in the fibrous system, hard, resisting,
dense and compact, hence the very great force which the organs of
this system have; hence, 1st, the solidity with which the vertebræ
are kept together; 2d, the difficulty of rupturing, or tearing the
fibro-cartilages of the knee, the jaw, the clavicle, &c.; 3d, the
resistance which that of the radius makes to the inferior luxations of
this bone, luxations which in the forced pronations of this bone have
great tendency to take place, and which cannot without the rupture of
this fibro-cartilage. I have seen an example of a similar displacement
not reduced; the fibro-cartilage was entirely gone; 4th, by bending
the true cartilages they break nearly like a radish; these organs
on the contrary bend in all directions, and resist the agents that
stretch them; 5th, we see men imprudently raise children by their
ears, the fibro-cartilages of which easily support the weight of the
whole body. I am persuaded that those of the nose would do the same.
6th. We know that in the aneurisms of the pectoral or the abdominal
aorta, the bodies even of the vertebræ are much more quickly worn, and
consequently resist less than the substances which unite them.
The cartilaginous portion appears to be interposed between the fibres,
the interstices of which it fills. It is very evident especially in
the articular fibro-cartilages and in those of the grooves; it is
from it that they borrow the white colour that characterizes them,
the inorganic appearance that a section of them exhibits in many
places, and the elasticity which they have. Subjected to ebullition,
the articular fibro-cartilages, like those of the tendinous grooves,
become yellow, transparent, melt into gelatine, though with much more
difficulty than the true cartilages.
As to the membranous fibro-cartilages of the ear, the nose, the
trachea, the epiglottis and the eye-lids, their composition appears to
be very different. The action of boiling water does not reduce them to
a gelatinous state, at least in an evident manner; they remain white,
soften a little, appear wholly different from a fibrous organ or the
other fibro-cartilaginous organs boiled, which dissolve after becoming
yellow and semi-transparent. The inspection of the ears of animals
that are brought on our tables clearly proves this; I have frequently
confirmed it in my experiments. I know but few of the textures in the
economy that resemble this. When it has been boiled a little while, the
kind of periosteum which surrounds it is detached from it; it breaks
itself and cracks in many places; the rings of the trachea especially
exhibit an example of this last phenomenon.
Exposed for some days to maceration, this texture, from being white,
becomes of a very evident red. This colour is deeper than that which
the cartilages of ossification acquire in water; does it arise from
the same causes? I know not.
When the intervertebral fibro-cartilages are macerated, their fibrous
laminæ take also their reddish tinge, which I have not seen in the
other articular fibro-cartilages, especially in those of the knee.
Drying makes the membranous fibro-cartilages hard and brittle; they do
not take then the yellow colour of the dried tendons and aponeuroses;
they have a peculiar appearance.
Subjected to this experiment, the intervertebral substances acquire
a remarkable transparency, different also from that of the fibrous
system, without the yellowish tinge. In the first days of their
maceration, these substances, when they have been entirely detached
from the vertebræ, swell, rise up and form a kind of hollow cone, the
summit of which is made by the middle which especially swells, and the
base by the circumference which remains nearly in the natural state.
Most of the fibro-cartilages want in general the perichondrium; this
is evident in those of the tendinous grooves in which the bone on one
side and the synovial membrane on the other cover the organ, in those
of the articulations which this membrane surrounds on both sides, and
in those of the vertebræ to which only the anterior and posterior
vertebral ligaments correspond. As to the membranous fibro-cartilages,
there is upon them a very distinct fibrous texture; it is thick,
closely united to the peculiar texture of the organ, easily seen by
maceration, which whitens it in an evident manner, and which thus makes
it wholly different from the fibro-cartilaginous texture which is in
the middle. By cutting a fibro-cartilage of the ear, the nose, that of
the epiglottis, &c. after they have remained in water, this fact is
made very clear, especially during the period in which they have the
redness that I have pointed out.
The fibro-cartilaginous system appears to have nearly the same
relations with the digestive juices, as the fibrous and cartilaginous
systems, of the nature of which it partakes; it is altered with
difficulty by those juices in a crude state. Boiling, by softening,
makes it yield more to their action; it becomes then more digestible.
In general, it gives an aliment less proper for nutrition, than that
furnished by many other systems.
II. _Parts common to the Organization of the Fibro-cartilaginous
System._
The common organs of the fibro-cartilages are not very conspicuous; the
cellular texture is in small quantity, and so compact as hardly to be
distinguished; maceration however renders it apparent.
But little blood enters their vascular system in the ordinary state;
I convinced myself of this by dissecting an animal killed for the
purpose by asphyxia, a disease in which the blood accumulating in
the capillaries intermediate to the arteries and the veins, towards
the head especially, renders these capillaries very evident; but in
inflammation, which is however rare in the fibro-cartilages, they are
very much injected. We can trace no nerves in them.