The cleido-mastoid generally arises from the basi-occipital, and the pectoralis major is connected with the latissimus dorsi.
From the outer tuberculum extends the large crista superior (insertion of pectoralis major and of deltoideus major muscles).
The chief muscular mass, arising from the sternum in the shape of a U, is the pectoralis muscle; its fibres converge into a strong tendon, which is inserted upon the greater tubercle and upper crest of the humerus, which it depresses and slightly rotates forwards during the downstroke.
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