OF THE MEMBRANIFORM CARTILAGES. 355 



ARTICLE III. 

 OF THE MEMBRANIFORM CARTILAGES. 



564. The membraniform cartilages are those which Bichat 

 has placed in his fibro-cartilaginous system. They are very 

 thin, and possessed of great flexibility. 



They are the palpebral cartilages or tarsi, the cartilage of 

 the ear, those of the nostrils, the cartilage of the epiglottis, 

 the median cartilage of the tongue, and the cartilages of the 

 trachea and bronchi. 



These very thin cartilages are furnished with a perichondri- 

 um, which is very thick and very strong compared with them- 

 selves, and sends into their substance fibrous and cellular pro- 

 longations, some of which even pass entirely through them. 

 Their surface also is very uneven and porous. Maceration 

 continued for two or three months softens them, and reduces 

 them to the state of distinct fibrils at first, and finally into cel- 

 lular or mucous substance. 



They are very flexible, perfectly elastic, and much less 

 brittle and more tenacious that the other cartilages. Like the 

 preceding, they concur in forming organs or canals, of which 

 they preserve the form and caliber. They are rarely ossified, 

 and only at a very advanced period of life. The rings of the 

 trachea alone present a more or less extended ossification in 

 the adult. In cases of phthisis, however, the cartilaginous 

 arches of the bronchi have been found ossified. In gouty per- 

 sons also, and after inflammation of the ear, the cartilage of 

 that part has been seen to become bony. In the case of goitre, 

 and even without this cause of pressure, the cartilaginous rings 

 of the trachea are sometimes found compressed from one side 

 to the other, and their middle part bent at an angle. The same 

 change of form is also observed in the bronchi. 



