OP THE PURELY CELLULAR TISSUES. CARTILAGE. 



261 



Fig. 52. 



Section of Fibro-Cartilage ; showing disposition of car- 

 tilage cells, in areolae of fibrous tissue. 



of the nose, the semilunar cartilage of the eyelids, the cartilages of the larynx 



(with the exception of the epiglottis), the Cartilage of the trachea and its 



branches, the cartilages of the ribs (in Man), and the ensiform cartilage of the 



sternum; and it is seen also in the tem- 



porary cartilages, or those which are 



destined to undergo ossification. The 



fibrous structure is seen in all those 



Cartilages, which unite the bones by 



synchondrosis ; this is the case in 



the vertebral column and pelvis, the 



cartilages of which are destitute of 



corpuscles, except in and near their 



centres. In the lower Yertebrata, 



however, and in the early condition 



of the higher, the fibrous structure is 



confined to the exterior, and the 



whole interior is occupied by the 



ordinary cartilaginous corpuscles. 



The reticular structure is best seen 



in the epiglottis and in the concha 



auris; in the former of these, 



scarcely any trace of cartilage-cells 



remains ; in the latter, the fibrous network disappears by degrees towards the 



extremity of the concha, and the structure gradually passes into the cellular 



form. 1 



253. Cartilage (at least in its simplest form) is nourished without coming 

 into direct relation with the Blood through the medium of bloodvessels ; for 

 the cellular Cartilages are not penetrated by vessels in the healthy state ; and 

 although in certain diseased conditions they seem to become distinctly vascular, 

 yet the vessels do not extend into the substance of the cartilage itself, but are 

 restricted to the new tissue in which they are developed. Cartilages, however, are 

 surrounded by Bloodvessels ; which form large ampullae or varicose dilatations at 

 their edges or on their surfaces (Fig. 



53) ; and from these the Cartilages Fig. 53. 



derive tl^eir nourishment by imbibi- 

 tion, in exactly the same manner as 

 the frond of a sea-weed (the structure 

 of which is alike cellular) draws into 

 itself the requisite fluid from the sur- 

 rounding medium. In the thicker 

 masses of cartilaginous tissue, how- 

 ever, such as the cartilages of the 

 ribs, we find canals excavated at 

 wide distances from each other ; 

 which are lined by a continuation of 

 the perichondrium or investing mem- 



brane of the cartilage, and which thus allows its vessels to come into nearer prox- 

 imity with parts that would be otherwise too far removed from them. The ves- 

 sels, however, nowhere pass from the walls of these canals into the substance 

 of the cartilage. Similar vascular canals are found in the temporary cartilages, 

 near the points where the ossifying process is taking place ; this is well seen in 

 the long bones, towards their extremities. At an early period of fatal life, 

 there is no distinction between the cartilage that is ultimately to become the 



Vessels between the Articular Cartilage and attached 

 Synovial Membrane. 



1 See Mr. Toynbee's Memoir on the "Non-Vascular Tissues," "Phil. Trans.," 1841. 



