144 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



7. The muscles of the upper back and shoulder and back of the neck.- 



(Fig. 42.) 

 Rabbit: 



a) Latissimus dorsi. Turn the animal on one side, so that the side on whic 

 the muscles have already been dissected will be uppermost. The large ffc 

 muscle extending obliquely from the middle of the back to the fore limb is tt 

 latissimus dorsi. Origin, lumbodorsal fascia and posterior ribs; insertion, 

 the crest on the medial side of the humerus, the insertion covered by the che; 

 muscles; action, draws the arm caudad and dorsad. 



b) Anterior and posterior trapezius. These two muscles are the flat, thi 

 muscles covering the upper back and back of the neck anterior to the latissimu 

 dorsi. The posterior trapezius originates from the lumbodorsal fascia and th 

 neural spines of the thoracic vertebrae, and is inserted on the spine of the scapuk 

 Action, draws the scapula dorsally. The anterior trapezius originates on th 

 external occipital protuberance of the skull and ligament in the mid-dorsal lira 

 and is inserted on the metacromion process (which is very long in the rabbit) an 

 nearby muscles and fascia; action, draws the scapula and limb upward and foi 

 ward. The space between the two trapezius muscles is filled by a stou 

 fascia. 



c) Levator scapuli ventralis. This long slender muscle runs along the ventre 

 border of the anterior trapezius near its insertion, then diverges to its origi: 

 from the ventral surface of the skull at the suture between occipital and basisphe 

 noid; insertion, metacromion process in common with the anterior trapezius 

 action, pulls the scapula anteriorly. 



d) Rhomboideus. Cut across the middle of the bellies of the two trapeziu 

 muscles and the latissimus dorsi. The large thick muscle extending from th 

 vertebral border of the scapula to the mid-dorsal line is the rhomboideus 

 Origin, mid-dorsal ligament of the neck and succeeding neural spines; insertion 

 vertebral border of the scapula; action, draws scapula toward vertebral column 



e) Splenitis. A fairly broad but thin muscle on the back of the anterior par 

 of the neck under the anterior trapezius. (Running along its external surfac 

 is a narrow straplike muscle, the rhomboideus capitis, see below.) Origin 

 splenius, mid-dorsal line of neck and adjacent fascia; insertion, occipital regioj 

 of the skull and atlas; action, singly turns the head, together raise the head 



Under the splenius are the epaxial muscles, continuations of those ahead 

 noted in the lumbar region. 



/) Supraspinatus. The superficial muscular layer of that part of the scapul 

 anterior to the spine consists of the pectoralis minor, which sweeps over th 

 scapula to be inserted on the spine and vertebral border. Lift up its anterio 

 border and separate it from the muscle beneath it. This muscle is the supra 

 spinatus, filling the supraspinous fossa of the scapula. Origin, supraspinou 

 fossa; insertion, greater tuberosity of the humerus; action, extends the humerus 



