AXILLARY SPACE 



33 



downwards on the lateral surface of the serratus anterior and 

 is the nerve of supply to that muscle. It arises in the root of 

 the neck, from the brachial plexus, by three roots. The upper 

 two roots (one from the fifth cervical and the other from the 

 sixth cervical nerve) pierce the scalenus medius, and uniting 



^.^.M. scalenus medius 

 \l M. scalenus anterior 



Upper part of M. serratus 

 anterior 



Middle portion of 

 M. serratus anterior 



M. obliquus 

 externus 



FIG. 14. Serratus anterior muscle and origin of the external oblique muscle ; 

 the scapula is drawn away from the side of the chest. 



into one stem give off branches to the upper part of the 

 serratus anterior. The third root takes origin from the seventh 

 cervical nerve, passes in front of the scalenus medius, and runs 

 downwards for a considerable distance on the surface of the 

 serratus anterior, before it unites with the other part of the 

 nerve. The entire nerve, thus formed, can be followed to the 

 lower part of the serratus, giving twigs to each of its digitations. 

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