OF THE TARSUS. 311 



calcis to the outer side of the scaphoid bone. These two ligaments resemble 

 the letter Y, being blended together behind, but separated in front. 



The Inferior Calcaneo-scaphoid (Fig. 212) is by far the larger and stronger of 

 the two ligaments of this articulation; it is a broad and thick band of fibres, 

 which passes forwards and inwards from the anterior and inner extremity of 

 the os calcis to the under surface of the scaphoid bone. This ligament not only 

 serves to connect the os calcis and scaphoid, but supports the head of the astra- 

 galus, forming part of the articular cavity in which it is received. Its upper 

 surface is lined by the synovial membrane continued from the anterior calcaneo- 

 astragaloid articulation. Its under surface is in contact with the tendon of the 

 Tibialis Posticus muscle. 1 



The articulation between the astragalus and scaphoid is an arthrodial joint ; 

 the rounded head of the astragalus being received into the concavity formed 

 by the posterior surface of the scaphoid, the anterior articulating surface of the 

 calcaneum, and the upper surface of the calcaneo-scaphoid ligament, which fills 

 up the triangular interval between those bones. The only ligament of this 

 joint is the superior astragalo-scaphoid, a broad band, which passes obliquely 

 forwards from the neck of the astragalus to the superior surface of the scaphoid 

 bone. It is. thin and weak in texture, and covered by the extensor tendons. 

 The inferior calcaneo-scaphoid supplies the place of an inferior ligament. 



The /Synovial Membrane which lines the joint is continued forwards from the 

 anterior calcaneo-astragaloid articulation. This articulation permits of conside- 

 rable mobility ; but its feebleness is such as to allow occasionally of dislocation 

 of the astragalus. 



The Synovial Membranes (Fig. 213) found in the articulations of the tarsus 

 are four in number ; one for the posterior calcaneo-astragaloid articulation ; a 



Fig. 213. Oblique Section of the Articulations of the Tarsus and Metatarsus. 

 Showing the Six Synovial Membranes. 



second for the anterior calcaneo-astragaloid and astragalo-scaphoid articulations; 

 a third for the calcaneo-cuboid articulation; and a fourth for the articulations 

 of the scaphoid with the three cuneiform, the three cuneiform with each other, 

 the external cuneiform with the cuboid, and the middle and external cuneiform 

 with the bases of the second and third metatarsal bones. The prolongation 

 which lines the metatarsal bones passes forwards between the external and 

 middle cuneiform bones. A small synovial membrane is sometimes found be- 

 tween the contiguous surfaces of the scaphoid and cuboid bones. 



Actions. The movements permitted between the bones of the first row, the 

 astragalus and os calcis, are limited to a gliding upon each other from before 



1 Mr. Hancock describes an extension of this ligament upwards on the inner side of the foot, 

 which completes the socket of the joint in that direction. Lancet, 1866, vol. i. p. 618. 



