586 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
usually composed are present. 1. The anterior fasciculus or band is short and strong 
(e./’, fig. 40). It passes from the fibular malleolus downwards and forwards to the 
astragalus, crossing the upper end of the middle fasciculus. 2. The middle fasciculus 
(e./, figs. 40 & 41) is much stronger and longer than the first fasciculus. It arises 
from the extremity of the fibular malleolus, and passes downwards and backwards to 
the outer side of the calcaneum, being inserted between the hinder margin of the 
articulating surface of the joint and the posterior end of the os calcis. 3. The 
posterior fasciculus of the lateral ligament is intermediate in length between the 
anterior and middle slips; but it is as strong as the outer middle fasciculus. Its 
attachments are from the inner border of the fibular malleolus to the inferior hinder 
edge of the astragalus, being oblique in direction as in the Primates (e./°, fig. 41). 
There is an additional well-marked and separate accessory slip of the posterior 
fasciculus of the external lateral (p, fig. 41). Besides the ordinary thin fascia covering 
the synovial membrane of the joint posteriorly, the above strong fasciculus may be 
regarded as a posterior ligament of the ankle. Its fibular attachment is close to the 
posterior inferior ligament connecting the tibia and fibula together; and, with a direc- 
tion similar and nearly parallel to that of the third fasciculus of the external lateral, it 
is inserted into the posterior pit of the astragalus. Its function is like that of the third 
external lateral fasciculus—namely, an oblique check on the astragalus, preventing its 
shifting its position inwards, or proceeding too far backwards. 
Action. The anterior ligament, while admitting of the ginglymoid or hinge-joint 
movement of the ankle-joint, is sufficiently lax to allow of the semirotary action 
which happens when the foot is placed forwards and inwards, or backwards and out- 
wards. The anterior and posterior fasciculi of the external lateral ligament are 
respectively fixed joints from which the astragalus rotates obliquely upon the tibio- 
fibular extremities. The middle fasciculus binds the fibula and caleaneum together. 
Along with the anterior fasciculus the two limit the motion of the astragalus and os 
calcis upon each other. When the foot is advanced forwards and inwards, the middle 
band of the lateral ligament checks the progress of the foot, the caleaneum acting as 
a lever upon the astragalus or fulcrum, being stopped by its becoming tense. In all 
other movements of the foot its tendinous fibres are relaxed. 
Astragalo-calcaneal ligaments.—A\l four separate portions of ligament connecting 
the astragalus with the caleaneum may be noted for their strength. 
1. The external of these is broad, and passes between the advanced protuberances 
or heads of the astragalus and calcaneum. ‘This fasciculus is strengthened by super- 
ficial fibres. 2. The anterior internal fasciculus is uncommonly broad and strong, 
and is partly covered by the deep plantar fascia (a.c’, fig. 39). The fibres have an 
oblique direction downwards and backwards, uniting the heads of the astragalus and 
caleaneum. 3. The posterior internal fasciculus (a.c’, figs. 39 & 41) is rather narrower 
than the last, but equally short and strong. It fills the groove between the posterior 
