254 SKELETON. 



articulations; in the lungs, and form there fistulous passages; 

 very frequently on the surface of the spleen; in the pleura; in 

 the fibrous coat of the large arteries, particularly the arch of 

 the aorta; and in the semi-lunar valves of the same; in the ova- 

 rium, when it becomes dropsical; and also in many other parts 

 of the body. 



The cartilages which are found loose in the joints and float- 

 ing about there, begin, for the most part, in the fibrous struc- 

 ture* exterior to the synovial membrane; the latter is protruded 

 inwards by them, and gives them a covering resembling the 

 finger of a glove. As these bodies are small and rounded, 

 when they protrude into the joint the synovial membrane forms 

 a pedicle or base to them, which is finally ruptured, and then 

 the cartilage becomes loose. These bodies are generally ossi- 

 fied in their centre, of course they have gone through the usual 

 progress and phenomena of ossification. The other forms of 

 preternatural cartilage are much disposed to ossify in the arte- 

 ries, but not so much so in the other organs. In these cases 

 they are laminated and adhere by their surfaces, very closely, 

 to the contiguous structure, so as to be membranous. M. 

 Laennec has seen a cartilaginous transformation of the mucous 

 membrane of the urethra; M. Beclard of the mucous membrane 

 in the vagina, attended with prolapsus uteri, and also of the 

 prepuce of an old man who had a phyrnosis from birth. 



OF THE PERICHONDRIUM. 



All the cartilages, except the articular ones, are invested by 

 a membrane called perichondrium, (perichondre.) It is best 

 seen on the larynx, and on the cartilages of the ribs. Its struc- 

 ture is fibrous, and corresponds so fully with that of the peri- 

 osteum that it may be considered the same sort of membrane. 

 It is, however, less vascular than the periosteum, and adheres 

 to the cartilages with less force, owing to the fibrous connexion 

 between them being not so abundant. Bichat's experiments 

 prove that the cartilage is much less affected by the loss of this 

 membrane, than the bone is by that of the periosteum: its uses 

 are no doubt the same. 



* Beclard, Anat. Gen. 



