182 ARTICULATIONS. 



cartilage cell shrinks up, and is separated from its capsule by a well-marked interval. The car- 

 tilage cells arc usually round or oblong, sometimes flattened or fusiform. Each contains a nucleus, 

 furnished occasionally with one or two nucleoli. The nuclei vary from ^ sv to 5^5^ of an inch; 

 they sometimes contain fat globules, or appear converted into fat. The intercellular substance 

 is either homogeneous, or finely granular, or fibrous. 



In temporary cartilage, the intercellular substance is not abundant ; but the cartilage cells 

 are numerous, and situated at nearly equal distances apart. The cells vary in shape and size, 

 the majority being round or oval, and their nuclei are minutely granular. When ossification 

 commences in it, the cells become arranged in clusters or rows, the ends of which are directed 

 towards the ossifying part. 



In articular cartilage, the intercellular substance is more abundant than in the former variety; 

 it appears dim, like ground glass, and has a finely granular or homogeneous aspect. The cells 

 are oval or roundish, from j^j to 9 J 5 of an inch, the nuclei small and commonly vesicular, and 

 parent cells are frequently seen inclosing two or more younger cells. On the surface of the 

 cartilage the cells are numerous, and disposed in isolated groups of two, three, or four, the groups 

 being flattened, and lie with their planes parallel to the surface. In the interior, and nearer the 

 bone, they are less numerous, and assume more or less of a linear direction, pointing towards the 

 surface. This arrangement appears to be connected with a corresponding peculiarity of structure 

 in the matrix, and serves to explain the disposition which this form of cartilage has to break in a 

 direction perpendicular to the surface, the broken surface being to the eye striated in the same 

 direction. 



In the costal cartilages, the intercellular substance is very abundant, finely mottled, and, in 

 certain situations, presents a distinctly fibrous structure, the fibres being fine and parallel. 

 This is most evident in advanced age. The cells, which are collected into groups, are larger 

 than in any other cartilages of the body, being from s } 5 to ^ of an inch in diameter. Many 

 contain two or more clear transparent nuclei, and some contain oil globules. Near the exterior 

 of the cartilage the cells are flattened, and lie parallel with the surface ; in the interior, the cells 

 have a linear arrangement, the separate rows being turned in all directions. 



The ensiform cartilage of the sternum, the cartilages of the nose, and the cartilages of the 

 larynx and windpipe (excepting the epiglottis and cornicula laryngis) resemble the costal carti- 

 lages in their microscopic characters. 



Reticular cartilage. The epiglottis, the cornicnla laryngis, the cuneiform cartilages, the carti- 

 lage of the ear, of the eyelid, and of the Enstachian tube, are included in a separate class under 

 the name of " reticular," "yellow," or " spongy" cartilages. They are yellow, of a spongy texture 

 throughout, more flexible than ordinary cartilage, and not prone to ossify. This variety of 

 cartilage consists of an intercellular substance, composed of minute opaque fibres, which inter- 

 sect each other in all directions, and are so arranged as to inclose numerous small oval spaces, 

 in which the cartilage corpuscles are deposited. 



Articular cartilage forms a thin incrustation upon the articular surfaces of 

 bones, and is admirably adapted, by its elastic property, to break the force of con- 

 cussions, and, by^its smoothness, to afford perfect ease and freedom of movement 

 between the bones. Where it covers the rounded ends of bones, upon which the 

 greatest pressure is received, it is thick at the centre, and becomes gradually 

 thinner towards the circumference : an opposite arrangement exists where it lines 

 the corresponding cavities. On the articular surfaces of the short bones, as the 

 carpus and tarsus, the cartilage is disposed in a layer of uniform thickness through- 

 out. The attached surface of articular cartilage is closely adapted, by a rough, 

 uneven surface, to the articular lamella ; the free surface is smooth, polished, and 

 partially covered by a perichondrium, prolonged from the periosteum, a short dis- 

 tance over the cartilage ; in the foetus, an extremely thin prolongation of synovial 

 membrane may be traced over the surface of the cartilage, according to Mr. Tpynbee, 

 but, at a later period of life, this cannot be demonstrated. Articular cartilage in 

 the adult does not contain bloodvessels; its nutrition being derived from the 

 vessels of the synovial membrane which skirt the circumference of the cartilage, 

 and from those -of the adjacent bone, which are, however, separated from direct 

 contact with the cartilage by means of the articular lamella. Mr. Toynbee has 

 shown, that the minute vessels of the cancellous tissue, as they approach the 

 articular lamella, dilate, and, forming arches, return into the substance of the bone. 

 The vessels of the synovial membrane also advance forwards upon the circum- 

 ference of the cartilage for a very short distance, and then return in loops ; they 

 are only found on the parts not subjected to pressure. In the foetus, the vessels 

 are said, by Toynbee, to advance for some distance upon the surface of the cartilage, 

 beneath the synovial membrane ; but Kolliker, from more recent examination, 



