SECT. 24.] 



CARTILAGE TISSUE. 



49 



In old age, the matrix of certain true cartilages is apt to become 

 fibrous, and to resemble, in its chemical characters, that of reticu- 

 lar cartilages j which, coupled with the fact, that, in certain places 

 (especially in the arytenoid cartilages of Mammals) reticular and 

 true cartilages pass continuously into each other, proves that these 

 two kinds of cartilage are not decidedly separated from each other. 

 In old age, it is not at all unusual for the true cartilages to ossify, 

 vessels and medulla being at the same time developed in them. 

 The cartilages do not possess the power of regeneration, and icounds 

 of cartilage are not healed by cartilage-substance ; on the other 

 hand, accidental formations of cartilage are by no means rare. 



The different kinds of cartilage-tissue are the following: — 



a. Cartilage-tissue icithout any basal substance, or cartilage-cell- 

 parenchyma. To this head belongs the chorda dorsalis of embryos, 

 and of many fully developed fishes; further, many fcetal cartilages, 

 the cartilages of the 

 branchial laminae of 

 fishes, in part, and 

 those of the external 

 car of many Mammals. 



b. Cartilage-tissue 

 with a matrix. 



1. With a more homo- 

 geneous matrix, yielding 

 chondrin,truecartilage, 

 hyaline cartilage (fig. 1 5 ). 



Fig. 16. 



Fig. 15. 



Human cartilage-eel's, from the whitish layer of the cricoid 

 cartilage ; magnified 350 times. 



A piece of the human epiglottis; magnified 

 350 times. 



This is found in the larger cartilages 

 of the respiratory organs, in those 

 of the joints, in the costal and nasal 

 cartilages, as Avell as immediately 

 covering the bones in all sym- 

 physes and synchondroses, on the 

 sidcus ossis cuboidei, and in the car- 

 tilages of ossification in the foetus. 



2. With a fibrous connecting mass, 

 yielding little or no chondrin. Reticu- 

 lar cartilage. Yellow cartilage (fig. 

 1 6); fibro-cartilagesinpart, epiglottis, 

 cartil. Santoriniance, Wrisbcrgiance. 

 Cartilage of the ear and of the 

 Eustachian tube, intervertebral liga- 

 ments in part. 



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