232 



THE MUSCLES. 



Fig. 114. 



MUSCLES OF THE AXILLARY AND 

 CERVICAL REGIONS. 



1, Portion of the cuticularis colli ; 2, An- 

 terior portion of the mastoido-hume- 

 ralis ; 3, Posterior portion of ditto ; 4, 

 Sterno-maxillaris ; 5, Subscapulo-hyoi- 

 deus ; 6, Sterno-hyoideus 7, Sterno- 

 thyroideus ; 8, Scalenus ; 9, Sterno- 

 humeralis ; 10, Sterno-aponeuroticus j 

 11, Sterno-trochineus (pectoralis mag- 

 nus); 12, Portion of the fascia en- 

 veloping the coraco-radialis, receiving 

 part of the fibres of the sterno-trochi- 

 neus ; 13, Steruo-prescapularis ; 14, 

 Its terminal aponeurosis. 



Situation Composition. Thi s muscle 

 is situated between the two anterior 

 limbs, occupies the inferior surface of 

 the chest, and is formed by two por- 

 tions which adhere closely to each other, 

 but are yet perfectly distinct. Following 

 the example of Girard, we will describe 

 these as two particular muscles by the 

 names of sterno-humeralis, and sterno- 

 aponeuroticus. 



A. STERNO-HUMEEALIS. Form - 

 Structure. This is a short, bulky muscle, 

 flattened above and below, contracted at 

 its termination, and composed almost 

 entirely of thick parallel fibres. 



Direction and Attachments. It com- 

 mences on the anterior appendage and the 

 inferior border of the sternum, and is 

 directed obliquely backwards, downwards, 

 and inwards, to reach the anterior ridge 

 of the humerus, where it terminates by 

 an aponeurosis common to it, the mas- 

 toido humeralis, and the sterno-aponeuro- 

 ticus. 



Relations. It responds, by its ex- 

 ternal face, to the skin, from which it is 

 separated by a cellular layer, and to the 

 inferior extremity of the cuticularis 

 colli ; by its internal face, to the sterno- 

 aponeuroticus and sterno-prescapularis. 

 Its anterior border forms, with the mas- 

 toido-humeralis, a triangular space occu- 

 pied by the subcutaneous, or " plate," vein 

 of the arm. 



Action. It acts principally as an 

 adductor of the anterior limb. 



B. STERNO-APONEUROTICUS. Form 

 Structure Direction Attachments. A 

 very wide, thin, and pale quadrilateral 

 muscle formed of parallel fleshy fibres, 

 which arise from the entire inferior 

 border of the sternum, to pass at first 

 outwards, then downwards, and terminate 

 in the following manner : the anterior 

 fibres go to the aponeurosis which attaches 

 the mastoido-humeralis and sterno-hu- 

 meralis to the anterior ridge of the 

 humerus ; the posterior fibres are also 

 continued by a very thin fascia, which is 

 spread inside the limb to the external 

 face of the antibrachial aponeurosis. 



Relations. By its superficial face, 



