OF THE TARSUS. 309 



Pollicis, and, in the groove behind the external malleolus, the tendons of the 

 Peroneus Longus and Peroneus Brevis. 



The Arteries supplying the joint are derived from the malleolar branches of 

 the anterior tibial and peroneal. 



The Nerves are derived from the anterior tibial. 



Actions. The movements of the joint are limited to flexion and extension 

 There is no lateral motion. 



: V. AETICULATIONS OF THE TARSUS. 



These articulations may be subdivided into three sets : 1. Articulation of the 

 first row of tarsal bones. 2. Articulation of the second row of tarsal bones. 

 3. Articulations of the two rows with each other. 



1. ARTICULATION QF THE FIRST Eow OF TARSAL BONES. 



The articulations between the astragalus and os calcis are two in number 

 anterior and posterior. They are arthrodial joints. The bones are connected 

 together by three ligaments : 



External Calcaneo-astragaloid. Posterior Calcaneo-astragaloid. 



Interosseous. 



The External Calcaneo-astragaloid Ligament (Fig. 211) is a short strong fasci- 

 culus, passing from the outer surface of the astragalus, immediately beneath 

 its external malleolar facet, to the outer edge of the os calcis. It is placed in 

 front of the middle fasciculus of the external lateral ligament of the ankle- 

 joint, with the fibres of which it is parallel. 



The Posterior Calcaneo-astragaloid Ligament (Fig. 210) connects the posterior 

 extremity of the astragalus with the upper contiguous surface of the os calcis ; 

 it is a short narrow band, the fibres of which are directed obliquely backwards 

 and inwards. 



The Interosseous Ligament forms the chief bond of union between the bones. 

 It consists of numerous vertical and oblique fibres, attached, by one extremity, 

 to the groove between the articulating surfaces of the astragalus ; by the otheii 

 to a corresponding depression on the upper surface of the os calcis. It is very 

 thick and strong, being at least an inch in breadth from side to side, and serves 

 to unite the os calcis and astragalus solidly together. 



The Synovial Membranes (Fig. 213) are two in number: one for the posterior 

 calcaneo-astragaloid articulation ; a second for the anterior calcaneo-astragaloid 

 joint. The latter sy no vial membrane is continued forwards between the con- 

 tiguous surfaces of the astragalus and scaphoid bones. 



2. ARTICULATIONS OF THE SECOND Row OF TARSAL BONES. 



The articulations between the scaphoid, cuboid, and three cuneiform are 

 effected by the following ligaments : 



Dorsal. Plantar. Interosseous. 



The Dorsal Ligaments are small bands of parallel fibres, which pass from 

 each bone to the neighboring bones with which it articulates. 



The Plantar Ligaments have the same arrangement on the plantar surface. 



The Interosseous Ligaments are four in number. They consist of strong trans- 

 verse fibres, which pass between the rough non-articular surfaces of adjoining 

 bones. There is one between the sides of the scaphoid and cuboid ; a second 

 between the internal and middle cuneiform bones; a third between the middle 

 and external cuneiform; and a fourth between the external cuneiform and 

 cuboid. The scaphoid and cuboid, when in contact, present each a small 

 articulating facet, covered with cartilage, and lined either by a separate synovial 

 membrane, or by an offset from the common tarsal synovial membrane. 



