4l« A MANUAL OF ANATOMY 



muscles about i inch from the base of the scapula. The disposition of the 

 rhomboideus major at its insertion is to be noted, and the fibrous band or arch 

 shown. The levator anguli scapulae is to be divided about its centre, and the 

 rhomboids about i inch from the spines of the vertebrae, which will bring into 

 view the posterior scapular artery lying close to the base of the scapula. A 

 branch to the levator anguli scapulae from the nerve to the rhomboids is 

 to be looked for, and a very hmited view will be obtained of the posterior 

 belly of the omo-hyoid at the upper border of the scapula. In association 

 with it the suprascapular nerve and artery may just be seen, but this dissection 

 is not to be pushed. 



The serratus posticus superior is next to be dissected, followed by that of 

 the serratus posticus inferior, and before reflecting these muscles the vertebral 

 aponeurosis is to be studied, and the posterior lamina of the lumbar apo- 

 neurosis, which gives origin to the latissimus dorsi and serratus posticus 

 inferior. At this stage the internal or deep surface of the serratus magnus 

 is to be examined. The serratus posticus superior is to be cut about i inch 

 from the spines of the vertebrae, and each serration of the serratus posticus 

 inferior is to be divided just below the rib into which it is inserted. The 

 vertebral aponeurosis is also to be carefully removed. In this manner the 

 erector spinae muscle is exposed. Before dissecting this muscle, however, 

 the splenius is to be studied, in concert with the dissector of the head, and 

 divided about i inch from its origin. Underneath the splenius will be found 

 the complexus, the inner portion of which is known as the biventer cervicis, 

 and external to the complexus is the narrow, ribbon-like trachelo-mastoid or 

 transversalis capitis. The dissector should now replace over the lower part 

 of the erector spinae the posterior lamina of the lumbar aponeurosis, having 

 attached to it the latissimus dorsi and serratus posticus inferior. At the outer 

 border of the erector spinae he should notice a portion of the middle lamina of 

 the lumbar aponeurosis, of which more will come into view by raising the outer 

 border of the muscle. He will thus see that the lower part of the erector 

 spinae is enclosed in a sheath, the posterior wall of which is formed by the pos- 

 terior lamina, and the anterior wall by the middle lamina, of the lumbar 

 aponeurosis. The anterior lamina is not visible at this stage. The obliquus 

 internus abdominis may be seen to arise from the lumbar aponeurosis between 

 the iliac crest and the last rib. 



The dissection of the erector spinae is now to be proceeded with. The 

 separation between the outer and middle columns of the muscle will be ap- 

 parent a little below the twelfth rib as a cellular interval, through which nerves 

 emerge, and in line with which, higher up, nerves, accompanied bv arteries 

 and veins, also appear. Dealing first with the outer column, and dissecting it 

 from below upwards, the sUps of insertion of the ilio-costalis into the angles of 

 the lower six ribs are to be shown. These are then to be turned outwards, and 

 the slips of origin of the musculus accessorius lying internal to them are to be 

 displayed, followed by the slips of insertion of that muscle into the upper ribs. 

 The latter having been turned outwards, the slips of origin of the cervicaUs 

 a.scendens will be found, and this muscle is to be followed up into the neck, 

 where its three slips of insertion are to be brought out. In dealing with the 

 middle column the dissector should first artificially separate from it the inner 

 column, the connection between the two being very close, and he may at once 

 dispose of the inner column or spinalis dorsi. Its four fleshy and tendinous 

 origins below should be shown, and its tendons of insertion above, varying 

 from four to eight in number. The series of arches formed by the tendons o/ 

 this muscle should be noted. The middle column is next to be dissected, and 

 the two series of insertions of the longissimus dorsi shown, the outer, fleshy, 

 passing to the lumbar transverse processes and ribs, and the inner, round and 

 tendinous, passing to the lumbar accessory processes and thoracic transverse 

 processes. At the upper part of the back the dissector will find that the 

 longissimus dorsi is prolonged into the neck by the transversalis cervicis, and 

 to the head by the trachelo-mastoid. It is at this stage that the complexus 

 is most advantageously studied. This muscle having been cut high up by the 

 dissector of the head, the semispinalis dorsi and semispinalis colli are to be 



