MEDIAL BRACHIAL CUTANEOUS NERVE 



983 



The nerve to the subclavius (fig. 755) is a small twig which arises from the fifth nerve or 

 from the upper trunk of the plexus, but occasionally it receives additional fibres from the 

 fourth and sixth nerves. It runs do^Tiward in front of the lower part of the plexus and the third 

 stage of the subclavian artery and, after giving off sometimes a branch to the phrenic, pierces the 

 posterior la5^er of the coraco-clavicular fascia, and enters the subclavius at its lower border. 



Variety. — In rare cases the entire phrenic nerve may pass vid the nerve to the subclavius 

 in front of the third stage of the subclavian artery. 



The scaleni and longus colli (figs. 751, 754) are supplied by twigs which arise from the lower 

 three or four cervical nerves immediately after their exit from the intervertebral foramina. 



The lateral branches of the infra-clavicular portion of the brachial plexus 

 are the anterior thoracic nerves, from the lateral and medial cords respectively, 

 the medial antibrachial (internal) cutaneous and the medial brachial (lesser 

 internal) cutaneous nerves, from the medial cord, and the subscapular nerves 

 and thoraco-dorsal from the posterior cord. 



The lateral anterior thoracic nerve joins with the medial to form a loop which 

 supplies the pectoralis major and minor. 



Fig. 



756. — Distribution of Cutaneous Nerves on the Anterior .\nd Posterior Aspects 

 OF THE Superior Extremity. 



Medial anti- 

 brachial 

 cutaneous 



Palmar cutaneous of 

 median 



Palmar cutaneous of 

 ulnar 



Supra -acromial 



Lateral brachial 



cutaneous 

 Intercosto- 



brachial 

 Twig of medial 



antibrachial 



cutaneous 



Dorsal 

 antibrachial 

 cutaneous 



Lateral anti- 

 brachial 

 cutaneous 

 (musculo- 

 cutaneous! 



Supraacromial 



Superficial 

 radial 



Ulnar 



It arises from the lateral cord of the plexus and contains fibres from the fifth, sixth, and 

 seventh cervical nerves (figs. 751, 754, 755). After joining the medial anterior thoracic it pierces 

 the coraco-clavicular fascia and ends in branches that supply the pectorahs major muscle. 

 The medial anterior thoracic nerve arises from the medial cord (figs. 751, 754, 755), contains 

 fibres from the eighth cervical and first thoracic nerves, and passes forward between the first 

 stage of the axillary artery and the axillary vein. It unites with a branch from the lateral 

 anterior thoracic, to form a loop which is placed in front of the first stage of the axillary artery; 

 it gives branches to the pectorahs minor, and branches which pass through the latter muscle and 

 end in the pectoralis major. From the loop additional branches are furnished to the pectorahs 

 major. 



The medial brachial (lesser internal) cutaneous nerve, or nerve of Wrisberg 

 (fig. 754), arises from the medial cord of the brachial plexus and sometimes con- 

 tains fibres from the eighth cervical and first thoracic nerves, but usually fibres 



