THE FABRIC OF THE HUMAN BODY, BOOK I.

Cartilage is more flexible than bone.

...[nature], and a more yielding temperament than that which falls to the lot of bones, it follows that the cavities they form are allowed to dilate and contract more readily than if they were rigid and hard in the manner of bone. And so, by virtue of this utility, the cartilages of the windpipe original: asperae arteriae; literally "rough artery," the historical term for the trachea, which represent the shape of a "C," differ from bones in this: that besides supporting the structure well, they can be compressed and distended without the need for various joint connections,

b Figures 14, 15 at the end of Chapter 38.

The use of cartilage in joints.

unlike bones. Add to this another use of cartilage, by no means the least, by which it provides the opportunity for bones to be less damaged by friction during continuous and frequent movements. For the connections commissurae; the points where bones meet of bones, constructed for the sake of movement, would be broken with little effort due to the dryness of the bones and their mutual contact, unless the bones—in every place where they touch one another and form a joint—were covered separately by a certain cartilaginous crust. This cartilage, by its own temperament of hardness and softness, resists the impact of the bones and, by yielding slightly, simultaneously dissolves the force of the collision. Nor is cartilage advantageous only in the clash of bones to prevent them from wearing down through mutual contact; it is also seen to be so smooth and flat that the head of a bone may roll most readily in its socket, and no roughness may hinder the promptness of movement—especially with the addition of a viscous and slippery fluid original: humore; Vesalius is describing synovial fluid, much like a kind of grease original: smegmate; an ointment or cleansing agent with which we smear wheels and hinges so that they are rendered more fit for turning. Indeed, the wise Maker of things a reference to God or Nature as the "Opifex" knew that the use of cartilage in joints would be so excellent that He not only encrusted the bones in mutual contact with smooth and slippery cartilage in the manner we have described,

A third cartilage in certain joints.

but in some joints, for the sake of certain specific movements, He applied a third kind of cartilage. This is not fused to the cartilage of either bone, but is born in a circular fashion only from the membranous ligaments of the joint, and it forms a sort of space interstitium between the cartilages covering the bones. On both sides where it sits between the other cartilages, it is smooth and slippery, and much softer than those cartilages that grow upon the bones (so that it may be compressed and rise up again more readily).

i Inserted in Figure 1 of Chapter 10.

k Figure 4, Chapter 22, letter S. l Figure 4, Chapter 22, letter R. m Figures 1, 2, 3, Chapter 24, letter T. n Figure 8, Chapter 31.

You will hear in the proper place how this kind of cartilage comes between the joints of the lower jaw and the temporal bones; then another in the joint of the breastbone with the collarbone the sternoclavicular joint, and the connection of the collarbone with the upper process of the shoulder blade the acromion, and of the ulna with the wrist, and of the shin bone the tibia with the thigh bone the femur. In this last joint, cartilages of this kind the menisci, by the great providence of Nature, specifically enlarge the sockets in which the heads of the thigh bone are received. Thus, cartilage provides such utility in the joints. To this is added

Cartilage acting in the place of glue.

the fact that in many connections of bones not designed for movement, cartilage intervenes as if in the place of glue; as we observe happening in the connection of the pubic bones, and in children, in the coalescing of the appendage the epiphysis; the end of a long bone with the rest of the bone.

o In the figures of the complete bones, letter s.

p Book 2, chapter 40, figure 2, characters 2 and s.

Furthermore, we must deal again with the nature of "gluing" cartilage when we follow the differences of bone connections; just as the species of cartilage, which we will teach that cartilaginous ligaments

Cartilage entering the substance of ligaments.

sometimes form, will be discussed in the description of ligaments. There are things of this kind in the

q In the same figure, character 3.

r Book 2, chapter 40, figure 2, P.

structure of the vertebrae of the body, in the hip joint, and in the knee. Moreover, certain cartilages

Cartilages keeping something continuously upright.

are fashioned for this: so that something within them which ought to be continuously erect may be strengthened.

s Book 1, chapter 1, figure X.

Of this kind are the cartilages of the eyelids, which support the upright hairs of the eyelids, or lashes; furthermore, the bare and protruding small parts of the body, and

Cartilages attached to protruding parts.

the ends of bones not joined to another bone, are increased by cartilage, so that they may consist of such a substance that can neither be broken because of its softness, nor snapped because of its dryness. Moreover, even children teach us that cartilage is formed of a substance no less [resilient] than nails; for when they have obtained a fairly large cartilage from a fish, or a calf's cartilage, they cut it into a small ball and throw it against a stone so that it bounces back most powerfully and frequently. For that bouncing clearly [demonstrates] the temperament of cartilage...

b 3