1062 DISSECTION OF THE UPPER LIMBS. 



within this circle the lactiferous ducts and sacculi will be brought into 

 view. 



Let the clavicular portion of the pectoralis major muscle now be divided 

 near the clavicle for the examination of the subclavicular space, preserving 

 the external anterior thoracic nerve as it passes to that muscle (p. 645) ; 

 and let the costo-coracoid membrane and sheath of the axillary vessels be 

 examined (p. 229). Then let the sheath be removed, and let the termi- 

 nation of the cephalic vein and the parts of the axillary artery and vein 

 brought into view be studied, and also the superior or short thoracic, 

 acromio-thoracic, and thoracico-humeral branches (pp. 377 and 468). 



For the dissection of the axillary space, the skin and the fascia are to 

 be separately raised from its surface (p. 230), and in the first place the 

 great vessels and nerves of the limb should be carefully exposed as they 

 pass from the axilla into the brachial region, but without much disturbing 

 their position. The axillary aitery and vein are then, to be followed 

 upwards, and the fat removed from within the space, when the long 

 thoracic vessels will be found chiefly along the anterior border, the sub- 

 scapular vessels principally along the posterior border, and the alar twigs 

 more in the middle. At this stage there will also be seen on the inner 

 wall of the axilla the intercosto-humeral with other lateral cutaneous 

 branches of intercostal nerves piercing the serratus magnus muscle (p. 657), 

 the posterior thoracic nerve descending on the surface of that muscle to 

 supply it (p. 644), and on the posterior wall the three subscapular nerves 

 (p. 645). When the axilla has been sufficiently studied, the remainder of 

 the pectoralis major muscle is to be divided ; the pectoralis minor muscle 

 also is to be dissected and divided, and the internal anterior thoracic nerve, 

 which supplies it, is to be found. By this proceeding the axillary vessels 

 TV ill be exposed in their whole course, and the origins of the branches of 

 the axillary artery may be more fully examined, viz., the acromio-thoracic, 

 the alar thoracic, short and long thoracic, and subscapular arteries, and the 

 anterior and posterior circumflex arteries. Three cords of the brachial 

 plexus will also be seen ; the outer one giving off the musculo-cutaneous, 

 the external anterior thoracic, and the outer head of the median nerve ; 

 the inner giving oft the inner head of the median nerve, the internal 

 cutaneous nerve, the nerve of Wrisberg, and the ulnar ; the posterior giving 

 off the three subscapular nerves, the circumflex, and the musculo- spiral 

 nerve. At this time, after removing the costo-coracoid fascia, the sub- 

 clavius muscle should be cleaned and examined (p. 206). 



On the fourth day after the subject has been placed upon its back, the 

 clavicle is to be sawn through the middle, or disarticulated at its sternal 

 end, if this should be recommended by the Demonstrator. The dissector 

 of the arm may then, in company with the dissector of the head and neck, 

 on the same side, obtain a continuous view of the upper part of the brachial 

 plexus, and trace the origins of the suprascapular and posterior thoracic 

 nerves (p. 641). The axillary vessels and the main trunks of the brachial 

 plexus of nerves are afterwards to be securely tied together opposite the 

 outer border of the first rib, and divided above the ligature ; the lower 

 parts may subsequently be retained in position, by tying them to the 

 portion of the clavicle left with the arm. The serratus magnus muscle may 

 now be put upon the stretch, and should be fully studied before the 

 removal of the arm (p. 207). 



3. Scapular Muscles, Vessels, and Nerves. After the arm has been 

 removed, the first duty of the dissector is to clean the parts which have 



