EXPLANATION OF THE PLATES. 



PLATE XXX. 



STRUCTURE OF CARTILAGE. 



Fig. 1. A transverse section of the cartilage of a rib, mag- 

 nified 350 diameters, showing the perichondrium 

 and the compressed cells of the margin of the 

 cartilage. It is most probable that it is in the 

 space between the perichondrium and the external 

 surface of the rib that the chief development of 

 new cells takes place. 



Fig. 2. A transverse section of the same, showing the parent 

 cells, which are situated more deeply in the car- 

 tilage of the rib. 



Fig. 3. A vertical section of the articular cartilage of the 

 head of the first phalanx of the second finger, in- 

 cluding also a portion of the bone, the cancelli of 

 which contain numerous bone cells, and the spaces 

 between which are filled with fat vesicles : magni- 

 fied 130 diameters. 



Fig. 4. A vertical section of the outer part of an inter- 

 vertebral cartilage, including a portion of the bone. 

 But few corpuscles, and these for the most part 

 calcified, occur in the outer part of these carti- 

 lages : the medullary cells of the bone are seen to 

 be filled with fat vesicles, granular nucleated cells, 

 and effused blood corpuscles. It sometimes hap- 

 pens that a layer of true articular cartilage is formed 

 on the surface of the bone, and then the fibres of 

 the fibro-cartilage take their origin from it, and not 

 from the bone itself: 80 diameters. 



