310 SKELETON. 



the tendon of the flexor pollicis. The middle arises from the* 

 pointed termination of the malleolus externus, and, descending 

 beneath the tendons of the peronei muscles, is attached to the 

 external face of the os calcis, below the surface for the astra- 

 galus. These fasciculi arc composed of strong longitudinal 

 and parallel fibres. The posterior is lander than either of the 

 others, and occasionally detaches a part which is inserted into 

 the posterior margin of the articular face of the tibia. 



The Synovial Membrane is reflected, as usual, over the arti- 

 cular surfaces, and from one bone to the other. It sends up a, 

 short process of a line in length between the tibia and the fibula, 

 it is remarkably loose in front and behind, and has on its super- 

 ficial face a considerable quantity of adipose matter, which can- 

 not be easily detached from it. It commonly contains an un- 

 usual quantity of synovia. 



Of the Articulations of the Foot. 



Of the Tarsal Articulations. }. The Os Astragalus is 

 united to the Os Calcis by a double articular surface, which has 

 been described. The ligaments which hold them together are 

 as follow: 



The Interosseous Ligament is pla-ced between the two bones, 

 so as te occupy the large oblique fossa between the double ar- 

 ticular surface in each. It is a collection of very strong, short 

 fibres, with interstices for fatty matter, which, arising from the 

 whole length of the groove in the astragalus, descends to be in- 

 serted into corresponding points in the groove of the os calcis. 

 Where the fossa is narrow, as it is behind, the ligament is thin 

 and flat, but it augments considerably in front, where there is 



more room for it. 







The posterior Ligament arises from the posterior margin of 

 the astragalus, and, descending obliquely inwards, is inserted 

 into the adjacent portion.of the os calcis. Its fibres, are blend- 

 ed with those of the Deltoid Ligament, and on their posterior 

 face they form a ligamentous trochlea for the tendon of the 

 flexor pollicis. 



