170 DISSECTION OF THE NECK. 



This ligament fixes the odontoid process of the second vertebra against 

 the body of the atlas, confining it in a ring (fig. 50). 



When the transverse and check ligaments have been cut through, the 

 tij> of the odontoid process will be seen to have two cartilaginous surfaces; 

 one in front where it touches the atlas, the other at the opposite aspect, 

 where it is in contact with the transverse ligament. Two synovial mem- 

 branes facilitate the movements of the odontoid process, one serving for 

 the joint between this piece of bone and the atlas; and the other for the 

 joint between it and the transverse ligament. 



Union of the articular surfaces. The articular surfaces of the occipital 

 bone and atlas are surrounded by a capsular ligament of scattered fibres, 

 which is strongest externally and in front. When the joint is opened, the 

 condyle of the occipital bone will be. seen to look somewhat outwards, and 

 the hollowed surface of the atlas inwards. A synovial membrane is pre- 

 sent on each side. 



The articular surfaces of the first two vertebra are inclosed on each side 

 by a capsule (fig. 46, 4 ), which is stronger in front than behind. On 

 opening the joint the surfaces of the bones may be perceived to be almost 

 horizontal. On each side there is a separate loose synovial membrane. 



Movements of the head. The head can be bent forwards and backwards; 

 turned from side to side rotation ; and inclined towards the shoulder. 



Nodding takes place in the joints between the atlas and the occipital 

 bone, the condyles gliding forwards and backwards. When the head is 

 moved more freely, flexion and extension of the cervical vertebras come 

 into play. 



Rotation is permitted by the several joints between the atlas and axis. 

 In this movement the axis is fixed, and the atlas, bound to it by the 

 transverse ligament, moves to the right and the left, carrying the weight 

 of the head. Too great a movement of the face to the side is checked by 

 the odontoid ligament. Only part of the whole of the rotatory movement 

 to one side is obtained between the atlas and axis, the rest being made up 

 by the neck. 



Approximation of the head to the shoulder is effected by the neck move- 

 ment: perhaps a very slight degree of it may be due to gliding downwards 

 of the occipital condyle of the same side on the articular surface of the 

 atlas. 



STERNO-CLAVICULAR ARTICULATION (fig. 51). The articular surfaces 

 are somewhat irregular and adapted to each other, with an intermediate 

 fibro-cartilage ; and they are retained in contact by a capsular ligament; 

 by a band to the first rib ; and by another band between the ends of the 

 clavicles. 



Dissection. For the examination of the ligaments of the sterno-clavicu- 

 lar articulation, take the piece of the sternum that was set aside for the 

 purpose (p. 134). If the ligaments have become dry, they may be moist- 

 ened for ;i short time. The several ligaments will appear in the situation 

 indicated by their names, after the removal of some fibrous tissue. 



Capsular liyament. This is a thin membranous expansion (fig. 51, a ), 

 M'hich incases the articular ends of the bones and the fibro-cartilage. It 

 is attached near the articular surface of eacli bone, and is thinner before 

 than behind. Sometimes the stronger fibres in front and at the back are 

 described as separate ligaments. 



The inter clavicular liyament (fig. 51, 3 ) extends above the sternum, 

 between the ends of the clavicles. The fibres do not cross in a straight 



