1094 



GENERAL ANATOMY OR HISTOLOGY. 



FIG. 621. Costal cartilage from, a man seventy- 

 six years of age, showing the development of fibrous 

 structure in the matrix. In several portions of the 

 specimen two or three generations of cells are seen 

 enclosed in a parent cell-wall. High power. 



ing to the shape of the articular surface on which it lies ; where this is convex the 

 cartilage is thickest at the centre, where the greatest pressure is received ; and the 

 reverse is the case on the concave articular surfaces. Articular cartilage appears 

 to derive its nutriment partly from the vessels of the neighboring synovial mem- 

 brane, partly from those of the bone upon which it is implanted. Toynbee has 



shown that the minute vessels of the can- 

 cellous tissue as they approach the articu- 

 lar lamella dilate and form arches, and 

 then return into the substance of the 

 bone. 



In costal cartilage the cells and nuclei 

 are large, and the matrix has a tendency 

 to fibrous striation, especially in old age 

 (Fig. 621). In the thickest parts of the 

 costal cartilages a few large vascular 

 channels may be detected. This appears, 

 at first sight, to be an exception to the 

 statement that cartilage is a non-vascular 

 tissue, but is not so really, for the vessels 

 give no branches to the cartilage sub- 

 stance itself, and the channels may rather 

 be looked upon as involutions of the peri- 

 chondrium. The ensiform cartilage may 

 be regarded as one of the costal cartilages, 

 and the cartilages of the nose and of the 

 larynx and trachea (except the epiglottis and cornicula laryngis, which are com- 

 posed of elastic fibro-cartilage) resemble them in microscopical characters. 



Temporary cartilage and the process of its ossification will be described with 

 bone. The hyaline cartilages, especially in adult and advanced life, are prone to 

 calcify that is to say, to have their matrix permeated by the salts of lime without 

 any appearance of true bone. The process of calcification occurs also and still 

 more frequently, according to Rollett, in such cartilages as those of the trachea 

 and in the costal cartilages, which are prone afterward to conversion into true 

 bone. 



White fibro-cartilage consists of a mixture of white fibrous tissue and cartilagi- 

 nous tissue in various propor- 

 tions ; it is to the first of these 

 two constituents that its flexi- 

 bility and toughness are chiefly 

 owing, and to the latter its elas- 

 ticity. When examined under 

 the microscope it is found to be 

 made up of fibrous connective 

 tissue arranged in bundles, with 

 cartilage-cells between the bun- 

 dles ; these to a certain extent 

 resemble tendon-cells, but may 

 be distinguished from them by 

 being surrounded by a concen- 

 trically striated area of cartilage 

 matrix and by their being less 



FIG. 622. White fibro cartilage from an intervvrtebral disc. 



flattened (Fig. 622). The fibro-cartilages admit of arrangement into four groups 

 mterarticular, connecting, circumferential, and stratiform. 



1. The interarticular fibro- cartilages (menisci] are flattened fibro-cartilaginous 

 plates, of a round, oval, triangular, or sickle-like form, interposed between the articu- 

 lar cartilages of certain joints. They are free on both surfaces, thinner toward their 

 centre than at their circumference, and held in position by the attachment of their 



