288 THE SOLIDS. 



tremities of the bones : in young children and sometimes 

 even in adults the synovial membrane which covers the free 

 surfaces of the cartilages also carries vessels which assist in 

 their nourishment. 



The independent or figured cartilages, as the ribs, &c., 

 are surrounded by a membraife, composed of condensed cel- 

 lular tissue, called the perichondrium : in this membrane the 

 vessels which afford nutriment to the enclosed cartilages 

 ramify. The ribs, moreover, contain grooves or canals, 

 which, commencing on the inner edge of the rib, first run 

 towards the centre, and then continue to pass forwards for 

 some distance : these canals also contain blood vessels. 



In the centre of ribs about to ossify a distinct medullary 

 canal containing blood vessels in abundance is clearly per- 

 ceptible. 



Vessels are also contained in the fatty masses enclosed in 

 some of the joints and called the glands of Havers ; from 

 these the adjacent cartilages doubtless imbibe a portion of 

 nutrient plasma. 



Amongst fibro-cartilages the synchondroses are stated to 

 receive vessels. Nerves have not, as yet, been discovered in 

 cartilages which may be irritated for any length of time 

 without the slightest pain being occasioned. 



During ossification, between the cartilage to be converted 

 into bone and that which is to remain as the articular 

 cartilage, a layer of vessels passes which, as the ossification 

 advances, gradually retire and wholly disappear soon after 

 birth. 



As cartilages do not contain vessels, they are not subject 

 to those disorders which depend upon errors of the circula- 

 tion ; that is, they are not liable to inflammation and its 

 consequences. Ulceration of cartilages is indeed described 

 by writers; but this term is wanting in accuracy when 

 applied to the erosion of which cartilages are susceptible, and 

 which is effected not through any operation occurring in the 

 cartilage itself, but through the action of vessels which, pro- 

 ceeding from the synovial membrane, dip down into the car- 

 tilage, and occasion its partial absorption. For the same 



