16 



DISSECTION OF THE UPPER LIMB. 



Remove fat 

 of axilla. 



Follow 



at the lower border on the right side, but at the upper border on 

 the left side. In the groove at the upper border, between the 

 pectoralis major and the deltoid, a small vein, the cephalic, 

 will be seen, and subjacent to this a small artery, the descending 

 or humeral branch of the acromio-thoracic, will be found running 

 downwards. 



The fascia and the fat are then to be taken from the axilla, 

 without injury to the numerous vessels, nerves, and glands in the 

 space. The dissection will be best executed by cleaning first the 

 large axillary vessels at the outer part, where these are about to 

 enter the arm, and then following their branches which are 

 directed to the chest, viz., the long thoracic under cover of the 

 anterior boundary of the armpit, and the subscapular along the 

 posterior boundary. With the latter vessels the middle and lower 

 subscapular nerves will be found, and just below them at their 

 origin, turning backwards near the hurnerus, are the posterior 

 circumflex artery and the circumflex nerve. Some arterial twigs 

 entering the axillary glands should also be traced out. 



In taking away the fascia and fat from the muscles at the back 

 of the space, the small internal cutaneous branch of the musculo- 

 spiral nerve (fig. 4 6 ) should be looked for near the great vessels. 



The nerves of the brachial plexus about the axillary vessels in 

 ^ e ou er p ar t of the space are then to be defined. The smallest of 

 these, which is commonly destroyed, is the nerve of Wrisberg ; it 

 lies close to the hinder edge of the axillary vein, and joins with the 

 intercosto-humeral nerve. 



and on inner Finally, when cleaning the serratus magnus muscle on the ribs, 

 the student will seek on its surface for the posterior or long 

 thoracic nerve (fig. 6 4 , p. 21) which runs down longitudinally 

 towards the back part of the muscle. The posterior offsets of the 

 intercostal nerves crossing the axilla will also be cleaned. 



Clean back 

 of space. 



Trace nerves 

 of plexus, 



wall. 



THE AXILLA. 



Situation 

 and form of 

 the armpit. 



The axilla is the hollow between the arm and the chest (fig. 4). 

 It is somewhat pyramidal in form, with its apex directed upwards 

 to the root of the neck. The space is larger near the thorax than 

 at the arm, and its boundaries are as follows : 



Boundaries : Boundaries. In front and behind, the space is limited by the 

 muscles passing from the trunk to the upper limb. In the anterior 

 wall are the two pectoral muscles, but these take unequal shares in 

 its construction : the pectoralis major (A*) extends over the whole 

 front of the space, reaching from the clavicle to the edge of the 

 anterior fold ; while the pectoralis minor (B) corresponds only to 

 about the middle third of the wall. 



In the posterior wall, from above downwards, lie the sub- 

 scapularis (F), the latissimus dorsi muscle (D), and the teres major (E) 

 muscles. The free margin of this wall, or the posterior fold, is 

 formed by the latissimus dorsi and teres major muscles, and is 

 * The letters and figures refer to fig. 4. 



anterior 

 wall : 



posterior 

 wall. 



