HANDBOOK OF PHYSIOLOGY. 



matrix is found in the human subject and in the higher animals gene- 

 rally, in early foetal life, when it constitutes the chorda dorsalis. 



Nutrition. Hyaline cartilage is reckoned among the so-called non- 

 vascular structures, no blood-vessels being supplied directly to its own 

 substance; it is nourished by those of the bone beneath. When hyaline 

 cartilage is in thicker masses, as in the case of the cartilages of the ribs, 

 a few blood-vessels traverse its substance. The distinction, however, 

 between all so-called vascular and non-vascular parts is at the best a 

 very artificial one. 



2. Yellow Elastic Cartilage. 



Distribution. In the external ear, in the epiglottis and cornicula 

 laryngis, and in the Eustachian tube. 



Structure. The cells are rounded or oval, with well-marked nuclei 

 or nucleoli (Eig. 48). The matrix in which they are seated is composed 

 almost entirely of fine elastic fibres, which form an intricate interlace- 



FIG. 47. FIG. 48. 



FIG. 47. Costal cartilage from an adult dog, sho mng the fat globules in the cartilage cells. 

 (Cadiat.) 



FIG. 48. Section of the epiglottis. (Baly. ) 



ment about the cells, and in their general characters are allied to the 

 yellow variety of fibrous tissue: a small and variable quantity of hya- 

 line and intercellular substance is also usually present. 



A variety of elastic cartilage, sometimes called cellular, may be ob- 

 tained from the external ear of rats, mice, or other small mammals. 

 It is composed almost entirely of cells (hence the name), which are 

 packed very closely, with little or no matrix. When present, the matrix 

 consists of very fine fibres, which twine about the cells in various direc- 

 tions and inclose them in a kind of network. Elastic cartilage seldom 

 or never ossifies. 



3. White Fibro-Cartilage. 



Distribution. The different situations in which white fibro-car- 

 tilage is found have given rise to the following classification: 



