MUSCLES OP THE SHOULDER AND ARM. 85 



Coccygeus, 6 /";w# the spine of the ischium and the lesser sacro-sciatic liga- 

 ment, into the margin of the coccyx and the side'of the last sacral segment. 

 Action, to support the coccyx, and close the outlet of the pelvis posteriorly. 

 Nerve, 5th sacral, anterior division. 



Sphincter Vaginae (in the female), from the central tendon of the perineum, 

 into the corpora cavernosa and body of the clitoris. Represents the accel- 

 erator urinae of the male. 



Erector Clitoridis (in the female), replaces the erector penis. 



MUSCLES OF THE SHOULDER AND ARM. 



Pectoralis Major, from the sternal one-half of the clavicle, by an aponeu- 

 rosis from the front of the sternum as low as the 6th or yth rib, the cartilages 

 of all the true ribs, and the aponeurosis of the external oblique, the fibres 

 converge, cross and are inserted by a flat tendon into the external bicipital 

 ridge of the humerus, having crossed the bicipital groove. Action, to draw 

 the arm forwards and downwards ; also to elevate the ribs in forced inspira- 

 tion. Nerves, anterior thoracic. 



Pectoralis Minor, from the 3d, 4th, and 5th ribs, and the intercostal aponeu- 

 rosis, into the coracoid process of the scapula. Action, to depress the 

 point of the shoulder, also to elevate the ribs in forced inspiration. Nerves, 

 anterior thoracic. 



Subclavius, from the cartilage of the 1st rib, into the under surface of the 

 clavicle, in a groove about its middle 3d. Action, to draw the clavicle 

 downwards. Nerve, a branch from the 5th and 6th cervical. 



Serratus Magnus, by 9 digitations/h?w the 8 upper ribs (the 2d rib having 

 2) and from the intercostal aponeurosis, into the whole length of the inner 

 margin of the posterior border of the scapula. Action, to elevate the ribs 

 in inspiration, also to raise the point of the shoulder. In lower animals 

 the great sling-muscle, slinging the body between the upper extremities. 

 Nerve, posterior thoracic. 



Deltoid, from the outer one-third of the anterior and superior surfaces of the 

 clavicle, the outer margin and upper surface of the acromion, and the whole 

 lower border of the spine of the scapula, into a prominence on the outer 

 side of the shaft of the humerus, about its middle. Action, to raise the arm. 

 Nerve, circumflex. 



Subscapularis, from the inner two-thirds of the subscapular fossa, into the 

 lesser tuberosity of the humerus. Action, to rotate the head of the humerus 

 inwards. Nerves, subscapular. 



Supra-spinatus, from the inner two-thirds of the supra-spinous fossa, intf 

 the upper facet of the greater tuberosity of the humerus. Action, to sup- 

 port the shoulder-joint, and to raise the arm. Nerve, supra-scapular. 

 8 



