42 ELEMENTARY TISSUES. 



With the exception of the articular variety, cartilage is 

 invested by a thin but tough and firm fibrous membrane 

 called the periclwndrium. On the surface of the articular 

 cartilage of the foetus, the perichondrium is represented by 

 a film of epithelium ; but this is gradually worn away up 

 to the margin of the articular surfaces, when by use the 

 parts begin to suffer friction. 



I. Cellular cartilage maybe readily obtained from the 

 external ear of rats, mice, or other small mammals. It is 

 composed almost entirely of cells (hence its name), with little 

 or no matrix. The latter, when present, consists of very fine 

 fibres, which twine about the cells in various directions and 

 enclose them in a kind of network. The cells are packed 

 very closely together, so much so that it is not easy in all 

 cases to make out the fine fibres often encircling them. 

 Cellular cartilage is found in the human subject, only 



in early foetal life, when it 

 constitutes the Chorda dor- 

 salis. (See chapter on Genera- 

 tion.) 



,., ; 2. Hyaline cartilage is met 

 with largely in the human 

 body, investing the articular 

 ends of bones, and forming 

 the costal cartilages, the nasal 

 cartilages, and those of the 

 larynx, with the exception of 

 the epiglottis and cornicula 

 larynyis. Like other cartilages it is composed of cells 

 imbedded in a matrix (fig. 14). 



* Fig. 14. A thin layer peeled off from the surface of the cartilage 

 of the head of the humeras, showing flattened groups of cells. The 

 shrunken cell-bodies are distinctly seen, but the limits of the capsular 

 cavities, where they adjoin one another, are but faintly indicated. 

 Magnified 400 diameters (after Sharpey). 



