42 MANUAL OF ELEMENTARY ZOOLOGY 



outline of its general arrangement and mention a few of 

 the more important muscles. 



The following table sets forth the general arrangement of 

 the muscular system : 



A. Muscles of the Trunk. 



I. Muscles of the lower side, 



a. Muscles of the Belly. 



e.g. Rectus abdominis, a wide band running along the 

 belly, divided lengthwise down the middle by the 

 connective tissue linea alba and transversely by 

 tendinous intersections. 



Obliquus extemus, a broad sheet at each side of the 

 body, arising from an aponeurosis known as the 

 dorsal fascia which covers the muscles of the back, 

 and inserted into the linea alba above the rectus 

 abdominis. 



Obliquus internus and transversus, muscular sheets 

 within the external oblique. 



By their contraction all these muscles lessen the size 

 of the body cavity and compress the organs within it. 



b. Muscles of the Breast Region. 



e.g. Pectoralis, large and fan-shaped, inserted into 

 the deltoid ridge of the humerus and consisting of a 

 sternal portion which arises from the pectoral girdle, 

 and an abdominal portion which arises from the 

 aponeurosis at the side of the rectus abdominis. 

 It draws down the arm. 

 Coraco-radialis, arising from the coracoid and inserted 

 into the upper end of the radius. It bends the 

 arm. 

 ■j.. Muscles of the Back. 



a. Muscle inserted into the Lower Jaw. 



Depressor mandibulce, triangular, arising from the 

 suprascapula and inserted into the angle of the lower 

 jaw, which it draws downwards and backwards, 

 thus opening the mouth. 



b. Muscles inserted on the Fore-Limb. 



e.g. Latissimus dorsi, triangular, arising from the 

 dorsal fascia and inserted into the deltoid ridge. 

 It draws back the arm. 



Infraspinatus, in front of and similar to the latissimus 

 dorsi. It raises the arm. 



c. Muscles inserted into the Shoulder Girdle. 



e.g. Levator scapula, arising from the skull and 

 inserted into the under side of the suprascapula, 

 which it draws forward. 



Serratus, arising from the little knobs on the transverse 



