ARTICULATIONS OF THE LOWER EXTREMITIES. 309 



is a large hole for transmitting the anterior tibial vessels, and 

 the origin of the tibialis posticus muscle. It also presents, in its 

 descent, several smaller foramina for the passage of vessels. Its 

 fibres are strong and unyielding, and run obliquely downwards 

 from the tibia to the fibula. It is covered in its whole length, 

 both before and behind, by muscles, and serves as an origin to 

 them and as a means of attachment between the hones* 



Of the Ankle Joint. 



The articular surfaces, here, being covered by cartilage as 

 in other moveable joints, are formed by the astragalus being 

 received into a deep cavity made by the tibia and the fibula. 

 The capsular ligament, properly speaking, does not exist ei- 

 ther on the front or the back of the joint, and is represented, 

 there, by a few scattered, loose fibres, on the periphery of the 

 synovial membrane. An internal and an external lateral liga- 

 ment, with the synovial membrane, constitute the whole appa- 

 ratus. 



The Internal Lateral Ligament, also called the Deltoid, (Lig. 

 Deltoideum) arises from the whole inferior margin of the mal- 

 leolus internus, and with particular strength from the depress- 

 ion which exists in it: it then descends and is inserted into the 

 internal face of the astragalus, and into the lesser apophysis of 

 the os calcis, which lies just below it. This ligament is broad, 

 thick, quadrilateral, and composed of fibres which descend 

 obliquely backwards. The tendon of the tibialis posticus runs 

 in a trochlea which is formed on the internal face of this liga- 

 ment. 



The External Lateral Ligament (Lig. Triquelrum) consists in 

 three distinct fasciculi, of which one is anterior, another pos- 

 terior, and the third in the middle. The anterior arises from 

 the lower extremity of the malleolus externus, and, running in- 

 wards and forwards, is inserted into the outer face of the as- 

 tragalus in front of the surface for the fibula. The posterior 

 arises from the depression in the extremity of the malleolus 

 externus, and, running inwards and backwards, is attached to 

 the point of the astragalus, at the outside of the groove, for 



