AXILLAEY REGION 327 



Origin. From the internal surface of the sacro-sciatic ligament, and 

 from the ischiatic spine. 



Insertion. Into the last sacral and the two first coccygeal or tail 

 bones. 



Action. This muscle forcibly depresses the tail. 



AXILLARY REGION 



Superficial Pectoral. Situated on the inner aspect of the arm. It 

 is broad above, and becomes narrower as it descends. In front it presents 

 a thick fleshy mass, while its posterior part is flat and thin. This muscle 

 forms the prominence so conspicuous in front of the breast. 



Origin. From the lower border of the sternum or breast-bone, where 

 its fibres are interwoven with its fellow on the opposite side. 



Insertion. Into the ridge in front of the humerus bounding the 

 musculo-spiral groove, and into the fascia covering the inner surface of the 

 arm. 



Action. To adduct or draw the limb inward towards the trunk, and to 

 tighten the fascia and brace the muscles of the arm. 



By some anatomists this muscle is divided into two parts, termed the 

 anterior and posterior superficial pectoral. 



Anterior Deep Pectoral. A long fleshy muscle extending from the 

 side of the sternum upward in front of the scapula or blade-bone. 



Origin. From the side of the sternum and the cartilages of the first 

 four ribs. 



Insertion. Into the fascia covering the external surface of the scapula. 



Action. To pull the scapula backwards and downwards. 



Posterior Deep Pectoral. This is a broad, flat muscle of consider- 

 able length. It extends from the under surface of the abdomen along the 

 side of the chest to the inner aspect of the arm. 



Origin. From the fascia covering the under surface of the abdomen 

 and the posterior part of the sternum. 



Insertion. Into the internal tubercle of the humerus, the tendon of 

 origin of the biceps, and the fascia which binds it down to the bicipital 

 groove. 



Action. To pull the scapula, arid with it the limb as a whole, in a. 

 backward direction. 



