352 GENEBAL ANATOMY. 



each side to these bones hy a kind of suture. Their edges, in 

 the interval between the bones, are intimately attached to ex- 

 ternal and internal periosteum, which passes from the one to 

 the other bone. Thus they greatly contribute to the solidity 

 of these articulations. These cartilages, in the sutures of the 

 skull, are thinner at the interior, than at the exterior of the 

 wall, which in pa-rt accounts for the quicker disappearance of 

 the sutures at the interior than at the exterior of the skull. 

 With respect to the frequency of their ossification, they are 

 intermediate between the temporary and the permanent car- 

 tilages. 



ARTICLE II. 

 OF THE COSTAL, LARYNGEAL, AND OTHER CARTILAGES. 



558. The costal cartilages* are the longest and thickest 

 cartilages of the body. They constitute cartilaginous prolon- 

 gations to the bony ribs. The first of them may also be con- 

 sidered as anterior or sternal cartilaginous ribs. The cartilages 

 are all attached to the anterior extremities of the ribs, like the 

 synarthrodial cartilages. The first is even continuous with 

 the sternum at the other extremity. The next six are articu- 

 lated with the sternum by diarthrosis. The three following 

 are in the same manner articulated with those which precede 

 them. The last two are immersed in the intermuscular cellu- 

 lar tissue. 



559. The texture of these cartilages is very obscure, and 

 at first sight they appear homogeneous. However, by macera- 

 tion prolonged for at least six months, the costal cartilages di- 

 vide into oval laminae or plates, separated from each other by 

 circular or spiral lines; and united together by some oblique 

 fibres which they send into each other. These laminae are 

 themselves divided into radiated fibrils, and the fibrils at length 

 into minute bundles, which are at length reduced into mucous 



* Heissant, Sur la. structure des cartilages des cotes de Fkomme et du cheval, 

 in Mm. de 1'acad. des sc., 1748. 



