CHAPTER II. 

 MUSCLES OF THE SHOULDER AND ARM. 



MUSCLES OF THE SHOULDER. 



Dissect off the skin together with the underlying skin 

 muscles from the neck, shoiilder and arm. Begin to 

 dissect from tJie dorsal side, placing the animal tipon 

 its right or left side. 



I. The Trapezius Muscle arises from the occipital 

 bone, and from the dorsal mid-line above the spi- 

 nous processes of the cervical and anterior thoracic 

 vertebrae. From this extensive line of origin the 

 fibres converge toward the scapula and humerus. Care- 

 fully cleaning the muscle from fat, fascia, etc., it will 

 be found to be composed of three divisions. 



a. The Anterior Trapezius is the most anterior 

 division ; it arises from the occipital bone, and from 

 the dorsal mid-line of the neck above the spinous pro- 

 cesses of all but the last cervical vertebrae. The mus- 

 cular fibres converge toward the humerus, where they 

 fuse with a long muscle, the levator humeri, and are 

 inserted with it into the lower part of the shaft of the 

 humerus. 



b. The Middle Trapezius arises from the dorsal 

 mid-line above the spinous processes of the posterior cer- 

 vical and anterior thoracic vertebrae in a continuous line 

 with the insertion of the anterior trapezius. Its fibres 



