550 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION, 
Rectus abdominis.—This altogether is a rather broad strip of muscle. Its narrower 
end (£.ad, fig. 33), that of origin, is from the os pubis, nearly its whole length, and 
in the median line. Proceeding forwards, and with its inner margin touching that of its 
fellow of the opposite side in the abdomen, it diverges slightly as it comes opposite the 
ensiform cartilage, and, then passing over the hinder free and sternal cartilages, has a 
fleshy insertion into the cartilage of the sixth rib. The external oblique and a few of 
the fibres of the internal oblique lie in front of or superficial to the rectus for about a 
distance of three or four inches from the pubis. ‘The remainder of the muscle, between 
the point spoken of and the thoracic cartilages, has the strong, fleshy transversalis and 
aponeurotic tendon of the internal oblique behind or placed deeply to it; but the external 
oblique remains superficial or covers it. It cannot be said that there is any distinct or 
strong fibrous tissue (the so-called sheath of the rectus) binding the muscles together. 
The latissimus dorsi (La.d, fig. 15) is a very broad, extensive, and powerful muscle. 
It arises from the middle line of the back, and also has digital slips of origin from the 
last seven ribs. There is little fascia in the spinal region; but what exceedingly thin 
muscular fibres there are, lie closely adherent to the serratus magnus and the long 
dorsal muscles. The fibres of the latissimus, as they proceed forwards on the chest, 
dip downwards and pass into the axilla behind, being inserted finally on the inner 
bicipital ridge. 
Serratus magnus (figs. 20, 21, S.mg).—On the thorax this muscle has attachments 
by serrations and slips to the anterior ten ribs; besides the form of the body, this 
circumstance gives the muscle an unusually elongated appearance. ‘The elongation 
of the muscle is increased as it runs up the neck as far as to the atlas, being inserted 
by muscular slips into each transverse process of the cervical vertebre ; the cervical 
muscular slips, however, are tolerably fused together, so that they form but one con- 
tinuous broad sheet. 
The serratus, as in Mammalia generally, has an insertion along the whole vertebral 
border of the scapula. There are two upper nuchal slips, however, which have an 
insertion quite on the dorsal surface and superficial to the remaining scapular insertion. 
These two slips just spoken of cover in part the supraspinatus muscle. The line of 
attachment of the serratus magnus to the side of the body and neck is a peculiar one ; 
and hence this muscle has by anatomists had its fibres divided into three or more sets, 
Commencing at the tenth rib, and continuing forwards, the fibres reach the atlas very 
little above the level of the posterior horizontal plane. 
Scaleni.—There are two scaleni muscles in the Sea-lion. That which answers to the 
scalenus posticus (fig. 21, Sea”) arises from the transverse process of the seventh cervical 
vertebra, and partly by a few fibres from the sixth, and, passing backwards, is inserted 
into the first rib. 
The scalenus anticus (Sca') has an origin almost identical with the above—namely, 
fibres from opposite the transverse processes of the sixth and seventh cervicals. This 
