CHAPTER V. 



JOINTS. 



THE various bones of which the skeleton consists are con- 

 nected together at different parts of their surfaces, and such 

 connections are called joints or articulations. 



In all instances some softer substance is placed between the 

 bones, uniting them together, or clothing the opposed surfaces ; 

 but the manner in which the several pieces 

 of the skeleton are thus connected varies 

 to a great degree. We distinguish three 

 varieties ; viz. those which are (1) immov- 

 able, (2) slightly movable, (3) freely 

 movable. 



The immovable articulations. The bones 

 of the cranium and the facial bones (with 

 the exception of the lower jaw) have 

 their adjacent surfaces applied in close 



contact, with only a thin layer of fibrous tissue or of cartilage 

 placed between their margins. In most of the cranial bones 



this union occurs by means of toothed 

 edges which fit into one another and 

 form jagged lines of union known as 

 sutures. The suture between the fron- 

 tal and parietal bones is called the 

 coronal suture; between the parietal 

 FIG.49.-AMIXEDARTICU- and occipital, the lambdoidal; and be- 

 LATION. a, 6, disk of fibro-car- tween the two parietal bones, along the 



tilage; c, articular cartilage; .^ j. Qn the t Q f the crown , 

 a, bone. 



the sagittal suture. 



The slightly movable or mixed articulation. In this form of 

 articulation the bony surfaces are usually joined together by 



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