TRANSVERSE TARSAL ARTICULATION. 647 



The superficial portion, Ugamentum longum plantce ( J ) is attached to 

 the under surface of the os calcis from near the posterior to the anterior 

 tubercle : its fibres pass forwards to be connected with- the ridge on the 

 under surface of the cuboid bone ; but the most internal are continued 

 over the tendon of the peroneus longus muscle, assisting to form its sheath, 

 and are inserted into the bases of the third and fourth metatarsal bones. 



The deep piece of the ligament (fig. 225, 5), seen on division of the 

 superficial, extends from the tubercle and the hollow on the fore part of 

 the under surface of the os calcis, to the cuboid bone internal or posterior 

 to the ridge. 



A simple synovial membrane belongs to the articulation. 



Articular surfaces. Both bones are flattened towards the outer part 

 of the articulation ; but at the inner side the os calcis is hollowed from 

 above down, and the os cuboides is convex to fit into it. 



Movement. In this joint the cuboid bone possesses two movements, viz., 

 an oblique one, down and in, and up and out. 



In the downward movement the internal lateral and the upper ligament 

 are made tight ; and in the upward, the calcaneo-cuboid ligaments of the 

 sole are stretched. 



TRANSVERSE TARSAL ARTICULATION (fig. 223). The joints of the 

 astragalus with the scaphoid, and os calcis with the cuboid bone, form a 

 transverse articulation across the foot in which the movements of inversion 

 and eversion take place. 



In inversion the great toe is adducted ; the inner border of the foot is 

 shortened, and is raised from the ground so that the sole looks inwards. 



The scaphoid bone passes down and in over the head of the astragalus, 

 being approximated near to the inner malleolus ; and the cuboid bone 

 moves down and in on the os calcis. The cuneiform bones are raised at 

 the same time and contribute to the movement (p. 648). 



The ligaments connected with both joints on the dorsum of the foot are 

 tightened. 



In eversion the inner border of the foot descends and lengthens, the 

 outer border is raised, and the great toe is abducted from the middle line 

 of the body. 



The same two tarsal bones are directed up and out, and the cuneiforms 

 sink. 



The ligaments in the sole of the foot of both joints now come into use 

 to prevent over movement. 



Dissection. Saw through the astragalus in front of the attachment of 

 the interosseous ligament between it and the os calcis; and remove the 

 head of the bone for the purpose of observing the lower and outer calcaneo- 

 gcaphoid ligaments. 



Then the interosseous ligament uniting the astragalus and the os calcis 

 is to be cut through, to demonstrate its attachments, the articular surfaces 

 of the bones, and the synovial sacs (p. 644). 



Articular surfaces of the two hinder tarsal bones. There are two 

 articular surfaces, anterior and posterior, to both the astragalus and the os 

 calcis. The hinder one of the os calcis is convex transversely and the 

 anterior is concave ; but sometimes the last is subdivided into two. The 

 surface of the astragalus will have a form exactly the reverse of that of 

 the os calcis, viz., the hinder one concave and the anterior convex ; the 

 anterior is seated on the head of the astragalus. 



