ANATOMY IX a NUTSHELL. 45 



Trapeszius. — Description. — (Plate XVIII.) This is a broad, Hat. trian- 

 gular muscle, placed immediately beneath the skin and fascia, and covering 

 the upper and back part of the neck and shoulders. It is fleshy in the •:• 

 part of its extent, but tendinous at its origin and insertion. At its origin, from 

 the spines of the vertebrae, it is connected to the bones by means of broad semi- 

 elliptical aponeurosis, which occupies the space between the sixth cervical and 

 the third dorsal vertebra, and tonus, with the aponeurosis of the opposite side, 

 a tendinous ellipse. 



Origin. — (1) by thin fibrous lamina' from the external occipital protuber- 

 ance and the inner one-third or one-half of the superior curved line of the occipi- 

 tal bone. (2)from the ligamentum nuchas. (3)from spinous processes of the seventh 

 cervical and all the dorsal vertebra 11 (4) and from the corresponding portion of 

 the supraspinous ligament. 



Insertion — (PlateXI-XX) — Thesuperior fibers pass downward and out- 

 ward and are inserted into the outer one- third of the posterior border of the clavicle 

 varing greatly in the extent of its attachment, sometimes advancing as far as 

 the middle of the clavicle, and may even become blended with the posterior 

 edge of the Sterno-mastoid oroverlapingit. The middle fibers pass horizontally 

 outward and are inserted into the inner margin of the acromion process and 

 superior lip of the posterior border or crest of the spine of the scapula. The 

 inferior fibers pass upward and outward, converging near the scapula, and ter- 

 minate in a triangular aponeurosis which glides over a smooth surface at the 

 inner extremity ofthe spine, to be inserted into a tubercle at the outer part of 

 this smooth surface. 



Action". — When this muscle acts as a whole it lifts the shoulder ami ro- 

 tates the lower angle of the scapula outward. The upper part raises the shoulder, 

 the middle part draws it toward the spine, and the lower pan in pulling the 

 scapula down and inward tilts the acromion process upward. If the shoulder 

 girdle i> fixed, this muscle will draw the head backward. 



Nerve Supply. — Spina! accessory and third and fourth cervical. 



Blood Supply. — Princeps cervicis from occipital, superficial cervical ami 

 posterior scapular from transversalis colli. 



LESSON IX. 



Scapula (Spade.)— (Plates XX-XXI.) — The scapula makes the posterior 

 pari of the shoulder-girdle, h is situated on the upper posterior part of the 

 thorax, between the second lib above and the seventh or eighth ribs below, 

 articulating with the clavicle by its acromion process laterally. 'This bone is 

 made up of several triangles; first, the main pari of the bone i> triangular with 

 two angles above and one below; the one n< \t to the vertebral column is called 

 the superior angle; the one n< ar< s1 the clavicle is called the anterior or external 

 angle and articulates with the humerus; the one near the seventh or eighth rib 

 is the inferior angle. Being a triangle it will have two surfaces and three bor- 

 ders, as well as three angles. The anterior surface or venter is concave, deepest 

 where the upper one-fourth joins the lower three-fourths; this is to give more room. 



