THE CONNECTIVE-SUBSTANCE GROUP. 45 



of the trachea and bronchia. The cartilage of the nose also 

 appears to be hyaline. 



The young, healthy, hyaline cartilage, but not that which 

 is growing old, is without vessels. 



An interstitial growth is evident ; the increasing size of the 

 cartilage cells, the expansion of the capsules, and the increase 

 of the intermediate substance remove every doubt. Is there, 

 besides, an increase of substance by apposition ? This is not 

 known. The nutrition takes place either from the blood- 

 vessels of a connective-tissue covering, the perichondrium, 

 or, when the cartilage envelopes the bone, from the adjacent 

 vessels of the latter. 



Elastic or reticular cartilages arise from a supplementary 

 metamorphosis, which commences during the embryonic pe- 

 riod. Their number is not large. Among these are the epi- 

 glottis, the Santorinian and Wrisbergian cartilages of the 

 larynx, the Eustachian tube, and the cartilage of the ear. 

 The arytenoid cartilages of the larynx and the symphyses of 

 the vertebras present the same peculiarity only partially. 



In reticular cartilage (Fig. 24) we generally meet with more 

 abundant cartilage cells, surrounded by a homogeneous area, 

 and the remaining intermediate substance permeated by a 

 close net-work of fine elastic fibres. Considerable variations 

 occur, however, in the different varieties of animals (Hertwig). 



By connective-tissue cartilage is denoted a substance which 

 presents small cartilage cells, surrounded by bundles of a con- 

 nective tissue which becomes homogeneous in acetic acid. 

 This variety is met with, for example, in the cartilaginous 

 lips of the joints, and locally in the vertebral symphyses ; 

 other parts of the latter present hyaline cartilage ; still others, 

 only ordinary connective tissue. In the so-called cartilages 

 of the eyelids only connective tissue can be recognized. 



We pass to the gelatinous tissue and reticular connective 

 tissue. 



Cartilage presented the quality of solidity ; gelatinous tis- 

 sue shows the character of softness in the highest degree. 

 Its most simple variety, the vitreus of the eye, is the richest 



