CHAP. IV.] CARTILAGE. 91 



sen ted in fig. 14, a, often exists, and seems to shew that this cover- 

 ing ceases when the part becomes subject to friction and pressure. 

 Cells, too, are often seen close to this surface, and even partly pro- 

 jecting from it; appearances indicative of attrition. 



In the cartilages of the ribs, which occupy an intermediate place 

 between the articular and membraniform varieties, the cells are 

 larger than in any other cartilage in the body, being from ^^ t TSO 

 of an inch in diameter. Many of them contain two or more nuclei, 

 which are clear and transparent; arid some seem to contain a few oil- 

 globules, a condition occasionally met with in other varieties. The 

 cells often affect a linear arrange- Ftg.is. 



ment. The rows of them are ^-ST 

 turned in all directions, and have 

 the appearance of having been 

 formed by the division of one cell, 



and the separation of its parts from JB/JH! 



each other. It is probable that V^" 



the splitting of the nucleus may mPJS&a k!ral 

 be the first step in this process, as, ^ > 

 for example, in fig. 15, a. 



The intercellular substance is 



very abundant in these cartilages; ^? " 



and though it usually presents, on 



a Section, a Very finely mottled Cartilage of the Ribs. Section shewing the cells, 



i , i their nuclei and nucleoli. The transparent spaces 



aspect, SUCh as IS Very Correctly resu lt from the removal of the cells by the knife, 



I ,i n t their cavities remaining. Magnified 320 diameters. 



pour tray ed in the figure, yet we 



may often discern in it a most distinctly fibrous structure, in which 

 the fibres are parallel, and which is most evident in the aged. 

 Perhaps it would be most correct to say that these fibres are only 

 formed by an artificial disintegration, for they are aggregated into 

 a solid mass in the unmutilated structure. They have very little 

 resemblance to the white fibrous tissue. Fig.it. 



It is not known whether they take any 

 constant direction. 



In the true membraniform cartilages, the 

 cells are very numerous in proportion to 

 the surrounding substance, which is conse- 

 quently in small quantity. This intercel- 

 lular matrix is very distinctly fibrous to- > T \* c^ 1 ?? 6 '- 111 section ' 



Magnified 320 diameters. 



wards the exterior of these cartilages, and 



often in their interior, but with considerable variety. The thyroid 



and rricoid cartilages, and the rings of the trachea, seem chiefly 



