3o6 A MANUAL OF ANATOMY 



The costo-coracoid ligament represents the ventral end of the coracoid bar 

 of cartilage, the dorsal end of which forms the coracoid process. 



Pectoralis Minor — Origin. — ^The upper borders and outer surfaces 

 of the third, fourth, and fifth ribs near their anterior extremities, as 

 well as from the fascia covering the adjacent external intercostal 

 muscles. 



Insertion. — ^The anterior half of the antero-internal border of the 

 coracoid process of the scapula and the adjacent portion of its upper 

 surface, where it is intimately connected with the common origin 

 of the coraco-brachialis and short head of the biceps. 



Nerve-supply. — ^The internal anterior thoracic nerve, which is a 

 branch of the inner cord of the brachial plexus, its fibres being 

 derived from the eighth cervical and first thoracic. The branches of 

 the nerve enter the muscle on its deep surface, and a few of them 

 pierce it to enter the deep surface of the pectoralis major. 



Blood-supply. — The thoracic axis. 



The direction of the fibres is upwards and outwards. 



Action. — Acting from its origin the muscle draws the scapula 

 downwards and forwards, the point of the shoulder being at the same 

 time depressed. Acting from its insertion it elevates the ribs from 

 which it arises, as in forced inspiration. 



Subclsivius— Origin. — By a rounded, tapering tendon from the 

 upper surface of the first rib and its cartilage. 



Insertion. — The subclavian groove on the under surface of the 

 clavicle, extending from the rhomboid impression internally to the 

 interval between the conoid tubercle and trapezoid ridge externally. 



Nerve-supply. — The nerve to the subclavius, which arises from the 

 front of the upper trunk of the brachial plexus, its fibres being 

 derived from the fifth cervical. The nerve descends from the neck 

 behind the clavicle, and enters the deep surface of the muscle. 



Blood-supply. — The thoracic axis. 



The direction of the fibres is upwards and outwards. 



Action. — (i) To depress the clavicle and draw it slightly forwards, 

 and (2) to support the sterno-clavicular joint by bracing the clavicle 

 in an inward direction. 



Axillary Space. — The axillary space is situated between the upper 

 part of the arm and upper part of the thoracic wall. It has the form 

 of a four-sided p5n-amid, and presents an apex, a base or floor, and 

 four walls — anterior, posterior, inner, and outer. It is of much 

 greater extent towards the thoracic wall than towards the arm, on 

 account of the convergence in the latter direction of the structures 

 forming the anterior and posterior walls. The apex is the narrowest 

 part of the space, and is directed upwards towards the root of the 

 neck. It is somewhat triangular, and lies between the clavicle, 

 first rib, and upper border of the scapula. The base or floor is of 

 considerable extent, and is formed directly by the axillary fascia, 

 which, as stated, is drawn upwards into the space by the clavi- 

 pectoral fascia. The anterior wall is formed over its whole extent 

 by the pectoralis major, and, under cover of this, by the pectoralis 



