The cartilages of the cavities have two different forms according to
the parts which they contribute to form. They are, 1st, long, as in the
ribs; 2d, flat, as in the larynx, the nasal partition, &c.
All are covered on the exterior with a fibrous membrane like the
periosteum, and in which different muscles are inserted. In order to
see this membrane it is necessary to macerate the cartilage for a day
or two; it then becomes white and very evident in its thickness, and
the direction of its fibres. The cartilages of the cavities do not
exhibit the numerous foramina which are seen in the bones, because the
blood vessels do not penetrate them. But few eminences and depressions
are observed in them. We can hardly consider their forms in a general
manner, because destined to very different uses, they have but little
resemblance in their conformation.