ARTICULATIONS AND LIGAMENTS. 129 



ferior surfaces of tibia and fibula, and consists of four: the 

 interosseous, continuous with that above; the anterior inferior 

 tibio-fibular, extending downward and outward between tibia and 

 fibula in front; the posterior inferior tibio-fibular, occupying 

 a similar position behind; and the transverse, a long narrow 

 band, passing between external malleolus and tibia. The syno- 

 vial membrane is continuous with that of ankle-joint. The 

 arteries and nerves are the same as those to the ankle. 



THE ANKLE-JOINT is a ginglymoid articulation, formed be- 

 tween the lower extremity and malleolus of tibia on the inner 

 side, the malleolus of the fibula on the outer side, and the as- 

 tragalus below. Its ligaments are anterior, posterior, external, 

 and internal lateral. 



The anterior tibio-tarsal ligament consists of a broad set of 

 irregular fibres, attached above to lower margin of tibia, below 

 to astragalus. The posterior tibio-tarsal ligament passes trans- 

 versely between back part of tibia and astragalus. 



The internal lateral, or deltoid, has two layers the super- 

 ficial triangular, its apex arising from malleolus, its base spread 

 out from before backward to be attached to scaphoid and infe- 

 rior calcaneo-scaphoid ligament, the sustentaculum, and inner 

 side of astragalus ; and the deep, a short, round cord passing 

 from internal malleolus to astragalus. 



The external lateral ligament consists of three distinct 

 fasciculi, anterior, middle, and posterior, arising from near sum- 

 mit of external malleolus, and being inserted respectively into 

 the front of astragalus, the outer surface of os calcis, and the 

 back of astragalus. 



The arteries of the ankle-joint are derived from the malleo- 

 lar branches of the peroneal and anterior tibial. 



Its nerves are branches of the anterior and posterior tibial 

 nerves. 



TlIE ARTICULATIONS OF THE TARSAL BONES Consist of those 



of the first row, those of the second row, and of the two rows 

 with each other. 



FIRST Row. The astragalus articulates with the calcaneum 

 by two distinct surfaces separated by the interosseous groove, and 

 firmly connected by the external and posterior calcaneo-astraga- 

 loid ligaments, and the interosseus. The external calcaneo- 

 astragaloid ligament passes vertically downward from the outer 

 surface of astragalus to outer surface of calcaneum. The pos- 

 terior is a short, narrow, oblique band connecting the posterior 

 border of astragalus to the os calcis. 



The interosseus is a strong, short ligament passing vertically 

 and obliquely downward between the tWQ bones ? the principal 

 bond Qf union, p 



