Ii6 THE MUSCLES. 



Insertion along an S-shaped line (Fig. 76, k-l) which 

 crosses the tuberosity of the scapular spine and forms an angle 

 with the spine of about forty-five degrees. The line extends 

 on one side onto the fascia covering the supraspinatus muscle, 

 and on the other side onto the fascia covering the infraspinatus, 

 but does not reach the borders of the scapula. The cranial 

 two-thirds of the insertion is by a flat tendon w r hich is broader 

 craniad. 



Relations. Outer surface with the cutaneus maximus, and 

 craniad with the acromiotrapezius (//). Inner surface with the 

 latissimus dorsi (;;/) caudad and with the rhomboicleus, supra- 

 spinatus, and infraspinatus craniad. Caudal border free; cranial 

 border in contact with the acromiotrapezius (//). 



Action. Draws the scapula dorsocaudad. 



M. acromiotrapezius, or trapezius superior (Fig. 68, /;). 

 The acromiotrapezius (middle part of the human trapezius) is 

 a flat four-sided muscle just craniad of the spinotrapezius, from 

 the median dorsal line to the scapular spine. 



Origin along the median dorsal line from the spinous process 

 of the axis to a point anywhere between the spinous processes of 

 the first and fourth thoracic vertebrae. Its caudal two-thirds is 

 from a flat tendon which is directly continuous with the muscle 

 of the opposite side and thus bridges the depression between 

 the vertebral borders of the scapulae. This tendon narrows 

 craniad, and its cranial fourth is attached by a fascia to the 

 spinous processes of the cervical vertebrae. At the cranial 

 border of the muscle the fibres sometimes reach the middle 

 line. The fibres of the muscle run nearly transversely. 



Insertion (Fig. 76, //). Into the outer surface of the meta- 

 cromion, the glenoid border of the scapular spine from the 

 metacromion to the tuberosity, and along a line continued for 

 about one centimeter from the tuberosity onto the surface of 

 the spinotrapezius (/) at the junction of its muscular and tendi- 

 nous portions. 



Relations. Outer surface with the cutaneus maximus, the 

 integument and platysma. Inner surface with a mass of fat 

 partially covering the rhomboideus ; with the occipitoscapularis, 

 spinotrapezius, supraspinatus, levator scapulas, and splenius. 



