DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 581 
The anterior ligament (fig. 29, @) has considerable thickness of fibrous tissue. It 
descends from the lower portion of the shaft of the humerus just immediately above 
the joint, and passes to the neck of the radius, but not to the ulna, which in Ofaria lies 
behind, and not, as usual, side by side with that bone. The anterior has, however, the 
ordinary union with the lateral ligaments, notwithstanding the aforesaid displacement 
of the bones. 
The posterior ligament (p, figs. 29 & 30) comes rather broadly from the back of the 
distal end of the humerus, and goes to the base of the olecranon, at which part it is 
contracted and narrow. 
The external lateral ligament is of considerable strength (e./, fig. 29). It passes from 
the external condyle to the outside of the neck of the radius. Although narrow, it is 
nevertheless, as said, a very strong tendinous band. 
The internal lateral ligament (7./, fig. 30) is much broader than the external lateral 
ligament, and is also very strong. It passes between the internal condyle and the 
inner, anterior, border of the ulna. It is also partly derived from the olecranon process, 
while below its fibres reach almost as far as the middle of the shaft of the ulna. 
Radio-ulnar ligaments.—The orbicular (orb, fig. 29) is very strong indeed where it 
joins the external lateral ligament. At this part it has the form of a broad band of 
glistening fibres. Its attachments are the lesser sigmoid cavity and the anterior neck 
of the ulna generally. 
The interosseous ligamentous union is not a wide, thin, aponeurotic membrane, as 
more ordinarily it is found to be, but here in the Sea-lion it is represented only by a 
narrow, nearly transverse, band of uncommonly strong and thick tendinous fibres. 
This band (7, figs. 29 & 30) passes between the shafts of the radius and the ulna about 
their middle, hinging, as it were, the one bone upon the other. 
Movements. ‘The position of the bones of the elbow-joint are such that the articu- 
lating surface of the humerus rests entirely upon the radius and very little on the ulna. 
The inner capitulum of the radius, furthermore, is flatly rounded, and so fits into the 
concave trochlea of the humerus that the two have very perfect freedom of rotation, 
the head of the radius thus being permitted to twist almost completely round its long 
axis. To this freedom of motion the force of stroke and feathering action of the fore- 
arm are mostly due. The ligamentous surface of the olecranon supports the humerus 
behind; and this surface presents a very shallow sigmoid notch, so that much side play 
to the ulna accrues. The coronoid process is unusually and relatively very small. It is 
so grooved outside that great freedom of motion is given to the head of the radius. The 
position of the ulna to the radius, and the looseness of the ligamentous articulation and _, 
ginglymoid nature of the interosseous band, allow the radius to be either alongside the 
ulna or quite anterior to it. The muscles, by thus being swerved round in conjunction 
with the altered positions of the bone, acquire additional force and power by their 
extra pulley. 
