558 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
from the superior rim of the scapula, from the angle half the length of the border, as 
far as the prominent part. In its course it overlaps and partly covers the subscapularis, 
and it is inserted into the capsular ligament ; but, besides, by a strong flattened tendon 
it is continued into the inner tuberosity, and there covers the insertion of the sub- 
scapularis muscle. This division of the supraspinatus is of great strength, and may 
be said regularly to roll round the (upper) anterior border of the scapula. It is 
apparently the same, I have found, in the Giraffe &c., and not identical with Mivart’s 
epicoraco-humeral in the Echidna. 
Action. ‘The supraspinatus proper with its double point of insertion acts as a direct 
extensor of the extremity on the scapula; but, furthermore, the additional longer inser- 
tion into the front of the great tuberosity, rolling round that humeral prominence, 
must add to the movement inwards of the arm—in fact, supplant the ordinary clavicular 
attachment of the deltoid, here wanting. The latter action is still further increased by 
the equally massive and more rounded direction of the fibres of the episubscapularis, 
the double insertion of which produces a longer lever. 
The infraspinatus (figs. 20, 27, J.sp), of an elongate wedge-shape, is, comparatively 
speaking, narrow. It barely covers the infraspinatus fossa, and is not very thick in 
fibre. As it passes downwards it has a partial attachment to, and, indeed, penetrates 
the capsular ligament, strengthening it, and resting on the shoulder-joint; but it is 
finally inserted by its broad, long, and strong tendon into the pit on the outside of 
the head of the humerus. 
Compared with the supraspinatus, the flexing power of the infraspinatus is greatly 
reduced ; its strong tendon entering the joint lends support to this otherwise weak and 
lax union. 
Subscapularis—This muscle is broad, corresponding in this respect with the propor- 
tionally wide and somewhat Cetacean-like character which the scapula itself possesses. 
The subscapularis muscle (5) overlaps both the superior and the inferior borders of the 
bone, and reaches the spinal border, except the posterior corner; it is inserted by a 
short but powerful tendon into the inner or lesser tuberosity of the head of the 
humerus. The exact point of its attachment is rather towards the upper part of the 
tuberosity. The double insertion of the episubscapularis covers that of the subsca- 
pularis on its axillary and anterior sides. ‘The thick flat fibres do not all run parallel 
with each other, but form two or more groups converging to a central line, or slight 
groove, wherein the vessels chiefly lie. 
Action. Tensor and fixer of the inner head of the humerus. The penniform 
arrangement of the fibres may alter the power either to the upper or lower border of 
the scapula, and in this way create a point d’appui for the powerful cephalo-humeral— 
latissimus dorsi and triceps, &c. Of course the power alters in the forward and back 
stroke ; subscapularis, therefore, is a kind of gearing to the bone, which does not receive 
support from its diminutive acromion and rudimentary coracoid processes. 
