FORMATION OF THE EPIPHYSIS OF LONG BONE. 233 



lage. In my preparations alluded to, page 236, a careful dis- 

 section shows branches running from the zone of vessels across 

 the head of the bone isolating the articular cartilage from the 

 epiphysal. These branches have beds of bone formed round 

 them, communicate freely with the vessels of the epiphysis, 

 but appear to send no branches towards the free surface of the 

 articular cartilage. The portion of the articular cartilage 

 immediately overlaying them, is however more tough and 

 periosteal in its character, than that on the free surface of the 

 cartilage, and has been, though not with exact propriety, 

 described by Mr. Listen, as cellular tissue connecting the carti- 

 lage and epiphysis. It is well known that in young subjects, the 

 articular cartilage is thick, and the compact layer of the epi- 

 physis below it thin and fragile ; while in old persons the com- 

 pact layer of the epiphysis is thick and strong, and the cartilage 

 covering is thin, rigid, and so firmly united to the bone below, 

 as to be with difficulty removed from it by the ordinary process 

 of cleaning. It would seem from this, that while the cartilage 

 gets its nutritive fluids by imbibition from the epiphysal vessels 

 and the marginal zone, some change is eflected by their passage 

 into its structure during the progress of life, by which the inner 

 portions of the articular cartilage is converted into bone. 

 Though in the healthy state no vessels can be injected in carti- 

 lage, in some diseases of the joints blood-vessels and granula- 

 tions may shoot up from the bone below into the place of the 

 cartilage. — It has been most probably in cases of this de- 

 scription, that the appearance of vascularity in the cartilages 

 has been observed; that of Mr. Liston, detailed in a late num- 

 ber of the medico-chirurgical transactions was from a diseased 

 joint. — 



The bones are retained in their relative situations by liga- 

 ments, such as have been lately mentioned, which are exterior 

 to the cavities of the articulations, and placed in such situa- 

 tions that they permit the motions the joints are calculated 

 to perform, while they keep the respective bones in their 

 proper places. 



20* 



