Cartilage is very well known under the name of 'gristle'; it is a tough, flexible, elastic substance found in every part of the body ; it has neither bloodvessels nor nerves.

Temporary cartilage is found in the skeleton of young subjects ; it is afterwards replaced by bone.

Permanent cartilage is of three varieties—hyaline, white fibro-, and yellow fibro-cartilage.

True or hyaline cartilage covers the ends of bones, where it is called articular cartilage ; it joins the ribs to the sternum, forming the costal cartilages ; it also enters into the formation of the nose, ear and throat.

In some parts of the body the connective tissue is more or less mixed with cartilage, and such tissues are called fibro-cartilage. White fibro-cartilage very much resembles while fibrous tissue. White fibro-cartilage is found in the discs between the vertebrae, in the glenoid and cotyloid ligaments, in the semi-lunar cartilages, sacro-iliac joint, symphysis pubis, and other articulations.

Fig. 11.—Ligaments of Elbow.

1, Capsular; 2, interosseous membrane.

Yellow or elastic fibro-cartilage is found in the epiglottis, the outer ear, and the Eustachian tube. It is tougher and more flexible than hyaline cartilage.

Fig. 12.—Ligaments of Shoulder.

1, Coraco-clavicular ; 2, coraco-acromial ; 3, coraco-humeral ; 4, capsular; 5, tendon of biceps.

Cartilage has very wide uses.

It forms smooth surfaces and lessens friction, as in joints.

It breaks shocks, acting as a buffer, as in the spine.

It gives elasticity, as in the walls of the chest.

It deepens cavities, as in the hip and shoulder joints.

It forms a firm framework, as in the larynx, outer ear and nose.

Articular cartilage depends for nutriment on the blood-vessels of subjacent bones and synovial membrane ; other cartilages are covered by a vascular fibrous membrane, called perichondrium, and receive nourishment from it.

Fig. 13.—Ligaments of Ribs and Sternum.

1, Ends of ribs ; 2, cartilages ; 3, ligaments joining cartilage ; 4, ligament uniting clavicle and first rib.