400 PRACTICAL ANATOMY. 



nor lip ofthe bicipital groove of the humerus with the major tereal muscle. These 

 two muscles, the trapezius and the latissimus dorsi, may now be removed by cut- 

 ting through their origins, tracing the same carefully to their respective inser- 

 tions, where they may be detached, when you will have exposed (Fig. 281) : 



1. The musculus levator anguli scapula;. 



2. The musculus rhomboideus minor. 



3. The musculus rhomboideus major. 



4. The musculus splenius capitis. 



5. The musculus complexus. 



6. The musculus serratus posticus inferior and superior. 



7. Vertebral aponeurosis. 



8. The occipital artery on the complexus muscle. 



9. The great occipital nerve. 



Now develop with scissors the four serrations of insertion into the lower four 

 ribs of the serratus posticus inferior. This muscle arises from the spines oi the 

 eleventh and twelfth thoracic, and the first and second dorsal vertebrae. Pull 

 the arm outward, and put the rhomboids on the stretch. Study their insertion 

 into the middle lip of the vertebral border of the scapula. Develop their 

 spinous origin. (Fig. 281.) 



Cut the rhomboids near their origins and turn them outward. (Fig. 281.) 

 See the nerve-supply on the under surface near the centre. See also the pos- 

 terior scapular artery, a continuation of the transversalis colli artery. 



The rhomboideus minor (Fig. 281) arises from the spine of the seventh 

 cervical and first thoracic vertebrae, and from the ligamentum nucha:. It is 

 inserted into the vertebral border of the scapula opposite the spine. Its nerve- 

 supply is from the brachial plexus. 



The rhomboideus major (Fig. 281) arises from the five upper thoracic ver- 

 tebras and their supraspinous ligament, and is inserted into the middle lip of the 

 vertebral border of the scapula from a point opposite the spine above to the in- 

 ferior angle below. The nerve-supply is from the brachial plexus. The action 

 of the rhomboids is to lift the scapula upward, backward, and inward. 



Levator Anguli Scapulae (Fig. 281). Pull the arm outward and find the in- 

 sertion of this muscle into the middle lip of the vertebral border of the scapula 

 above the spine. Trace its three or four tendons of origin to the anterior tubercles 

 ofthe transverse processes ofthe four upper cervical vertebrae. This muscle derives 

 its nerve-supply from the cervical plexus. Its action is to elevate the scapula 

 and, by producing rotation of the same, it depresses the point of the scapula. 



Serratus Posticus Superior (descending fibres) (Fig. 282). This muscle 

 lies under the levator anguli scapulae and rhomboids. It arises by aponeurosis 

 from the seventh cervical spine and the upper three dorsal spines. It is inserted 

 into the second, third, fourth, and fifth ribs, a little beyond the angle. The 

 nerve-supply is from the posterior primary divisions of the second and third 

 intercostals. 



The serratus posticus inferior (ascending fibres) (Fig. 282) arises, by 

 aponeurosis, from the two lower dorsal and three upper lumbar spines ; it is 

 inserted into the four lower ribs a little beyond the angle. Notice the difference 

 between the two serrati muscles. The upper is inserted into the upper border, 

 the lower into the lower border of ribs. 



The Vertebral Aponeurosis (Fig. 282). Internally you see this aponeurosis 

 attached to the spines ; externally it is attached to the angles of the ribs ; below 

 it blends with the serratus posticus inferior and latissimus dorsi ; above it passes 

 behind the superior serratus. It separates the proper muscles of the back from 

 those that act on the shoulder girdle. 



The Splenius Capitis and Colli. develop the long, pointed origin of this 



