644 



DISSECTION OF THE LEG. 



Fig. 222. 



all further motion is arrested by the meeting of the anterior edge of the 

 tibia with that bone. 



The posterior ligament is stretched over the projecting head of the 

 astragalus, and the posterior and middle parts of the external lateral, and 



the posterior piece of the internal 

 lateral ligament, are made tense. 



In extension the astragalus moves 

 forwards over the end of the tibia, 

 and projects anteriorly. A limit to 

 the movement is imposed by the meet- 

 ing behind of the astragalus with the 

 tibia. 



The lateral ligaments are partly 

 made tight as in flexion, for instance 

 the anterior piece of the external, and 

 the fore and middle portions of the 

 internal 



When the joint is half extended so 

 that the small hinder part of the as- 

 tragalus is brought into the arch of 

 the leg bones, a slight movement of 

 the foot inwards and outwards may 

 be obtained ; but if the foot is forcibly 

 extended the portions of the lateral 

 ligaments, attached to the astragalus, 

 prevent this lateral movement by 

 their tightness. 



Dissection. The joints of the foot 

 will be demonstrated by removing 

 from both the dorsum and the sole all 

 the soft parts which have been examined. Between the different tarsal 

 bones bands of ligament extend, which will be defined by removing the 

 areolar tissue from the intervals between them (fig. 223). 



It will be more advantageous for the student to clean all the ligaments 

 before he proceeds to learn any, than to prepare only the bands of one 

 articulation at a time. 



ARTICULATION OF THE ASTRAGALUS AND os CALCIS. These bones 

 are kept together by two joints, and a strong interosseous ligament ; and 

 there are also thin bands at the outer side and behind. 



The posterior ligament (fig. 223, ) consists of a few fibres between 

 the bones, where they are grooved by the tendon of the flexor pollicis ; 

 and the external ligament (b) is connected to the sides of the astragalus 

 and os calcis, near the middle piece of the external lateral ligament of the 

 ankle joint. 



The interosseous ligament (fig. 223, c) consists of strong vertical and 

 oblique fibres, which are attached above and below to the depressions on 

 the contiguous surfaces of the two bones. This band extends across the 

 bones, and its depth is greatest at the outer side. 



In a subsequent stage of the dissection (p. G47) articular surfaces will 

 be seen between the bones, viz., one behind the interosseous ligament, and 

 one in front of it, with two synovial membranes. 



Movement. Under the influence of the weight of the body, as in stand- 

 ing, the astragalus moves down and in (not straight forwards) with 



EXTERNAL LATERAL LIGAMENT OF THE 

 ANKLE (altered from Bourgery). 



1. Anterior part. 



2. Posterior part. 



3. Middle part of the outer ligament. 



4. Interosseus-of astragalus and os calcis. 

 o. External caluaueo-scaphoid ligament. 



