OF THE MUSCLES. 97 



supra spinalis, as far forward as the third cervical vertebrae ; 

 and as far backward as the fifth dorsal ; and is inserted into 

 the inner surface of the cartilage of the scapula. Action. 

 It aids the serratus magnus, as well as keeps the cartilage of 

 the scapula close to the trunk. 



Serratus magnus {Plate II. k). Origin. From the trans- 

 verse processes of the third, fourth, fifth, sixth, and seventh 

 cervical vertebrae ; from the entire length of the first, second, 

 third, and fourth ribs ; and into diminishing surfaces of the 

 fifth, sixth, seventh, and eighth ribs. Insertion. Into the 

 cartilage and venter of the scapula. It is that portion only 

 of this muscle which goes to the eighth, seventh, sixth, and 

 fifth ribs and digitates with the external oblique. Action. 

 To move the scapula in progression ; and also to enlarge the 

 chest, by drawing the true ribs forward and outward when 

 standing still. 



OF the anterior extremity. 



SuBSCAPULo-HYOiDEUs (Plate III. /i). Originates: ante- 

 riorly, by fibre from the spur process of the os hyoides. 

 Inserted : posteriorly by fine tendon to the inner side of 

 the shoulder. Action : to draw the os hyoides dowmwards ; 

 and to a slight extent to aid in pulling the shoulder forward. 

 The muscle passes between and over important parts, divid- 

 ing the jugular vein from the carotid artery ; and covering 

 the par vagum, sympathetic, recurrent, and phrenic nerves, 

 besides lymphatics and conglomerate glands. 



ScAPULO-ULXARius {Plate III. 1. Plate 11./. Fig 1.5). 

 Originates : by tendon from the olecranon ; and is inserted 

 into the posterior angle of the scapula. There is another 

 muscle inferioiiy situated, which usually is cut off with the 

 scapulo-ulnarius ; though it is distinct. Action. To flex the 

 scapula upon the humerus. 



Teres externus {Plate II. e) . Arises: from the spine of the 

 scapula ; and is inserted into the small trochanter, upon the 

 humerus. There is likewise an additional muscle, usually 

 separated with the teres externus. Action. This muscle 

 acts with the teres internus serving to flex the scapula 

 upon the humerus. 



Teres internus {Fig 1.3). Originates : from the poste- 

 rior angle of the scapula ; to be inserted into the body of 



H 



