LIGAMENTS OF THE VEETEBEAL COLUMN. 305 



the interior of an articular cavity except the articular encrusting cartilage. Conse- 

 quently the synovial stratum is absent only from the free surface of articular cartilage, 

 although it forms a thicker layer upon the inner surface of the articular capsule than 

 upon the free surfaces of interarticular ligaments, discs, and menisci. 



It is not necessary to suppose that the synovial stratum has disappeared from these 

 articular cartilages as the result of friction, because, notwithstanding constant friction, 

 such parts as the interior of articular capsules or the menisci of the knee-joint have not 

 been denuded of their synovial covering. 



As the epiphyses adjoining articular cavities are produced in the joint-units, the 

 attachments of the capsule should be found upon, and restricted to, the non-articular 

 surfaces of the articular epiphyses. While this is the case in their earliest stages; yet, as 

 development advances, considerable variations arise, until, in the adult condition, the 

 capsule of the larger articulations, more particularly of the extremities, is not always 

 restricted to the epiphyses for its attachments. The student will readily perceive and 

 appreciate these variations by comparing the accounts and illustrations of the epiphyses 

 with those of the articulations, and he should note that in some cases the epiphysial line 

 is extra-capsular, i.e. the capsular attachment is restricted to the epiphysis ; in some the 

 line is intra-capsular ; and in some the epiphysial line is partly in tra- capsular and partly 

 extra-capsular. 



MORPHOLOGY OF LIGAMENTS. 



From what has been said in connexion with the development of joints, it will be evident 

 that ligaments are essentially products derived from the cellular articular disc. 



Nevertheless, in relation to the fully formed joint, many structures are described as ligaments 

 which do not take origin in the manner just indicated. Some of these ligamentous structures 

 remain fairly distinct from the articular capsules with which they are immediately associated ; 

 others become thoroughly incorporated with the articular capsules and cannot be separated 

 therefrom, while yet others may be found situated within the capsule of a joint, and thus play 

 the part of interarticular ligaments. 



Instances of each of these forms of adventitious ligaments may be readily given. For 

 example, we may instance the expansion of the tendon of the semimembranosus muscle to the 

 oblique ligament of the knee-joint, and the offshoots from the tendon of the tibialis posterior 

 muscle to the plantar aspects of various tarsal bones, as illustrations of structures which play 

 an important part as ligaments, but are not indelibly incorporated with the joint capsule. 



Of structures which have become indelibly incorporated with the primitive capsule, we may 

 instance the broad tendinous expansions of the quadriceps extensor muscle around the knee-joint. 



The tibial collateral ligament of the same joint is regarded as a detached portion of the 

 tendon belonging to that part of the adductor magnus muscle which takes origin from the 

 ischium, while the fibular collateral ligament of the knee is considered by some to be the primi- 

 tive femoral origin of the peronoeus longus muscle. Another illustration of the same condition 

 is found in the coraco-humeral ligament, which is regarded by some as representing a detached 

 portion of the pectoralis minor muscle. 



Two illustrations may be given of structures playing the part of ligaments within the 

 capsule of a joint, although in the first instance they are not developed as ligaments. It is 

 questionable if the ligamentum teres of the hip-joint is an interarticular ligament in the true 

 sense of the term ; it has been regarded as the isolated and displaced tendon of the ambiens muscle 

 found in birds. In the shoulder -joint, many observers look upon the superior gleiio-humeral 

 ligament as representative of the ligamentum teres. 



Such structures as the stylo-hyoid ligament and the spheno-mandibular ligament, although 

 described as ligaments, are in reality skeletal parts which have not attained their complete 

 ossific development. 



Again, certain portions of the deep or muscular fascia of the body which become specialised 

 into restraining and supporting bands (e.g. the ilio-tibial tract of the fascia lata ; the stylo-mandi- 

 bular ligament ; the transverse carpal and dorsal carpal ligaments of the wrist-joint ; the 

 transverse crural ligament, and lig. laciniatum of the ankle-joint), although called ligaments, 

 have no direct developmental association with articular ligaments. 



Lastly, the inguinal ligament of Poupart and the lacunar ligament of Gimbernat, being 

 special developments in connexion with an expanded tendon or aponeurosis, are still further 

 removed from association with an articulation. 



LIGAMENTA COLUMNS VEETEBRALIS ET CRANIL 



Ligaments of the Vertebral Column and Skull. All vertebrse, with the 

 exception of those which deviate from the common vertebral type, present two 

 sets of articulations whose various parts are arranged upon a uniform pattern. 

 Thus, every pair of typical vertebrae presents an articulation between the bodies 

 and a pair of articulations between the vertebral arches. With the latter there 



20 



