THE AXILLA. 265 



Axillary abscesses, if of slow formation and unopened, tend to burrow and follow 

 the vessels upward beneath the clavicle and appear in the supraclavkular space beneath 

 the deep cervical fascia, and they may even enter the superior mediastinum. They 

 may also descend the arm under the fascia covering the coracobrachialis muscle. 



Axillary Tumors. Tumors of the axilla are almost always due to involvement 

 of the lymph-nodes. They may be either benign and inflammatory in character, form- 

 ing the ordinary axillary adenitis, or tuberculous, or they may be malignant. As 

 they are due to disease of the lymph-nodes, the parts which the glands drain should 

 be searched for the starting-point of the affection. Aneurism or abscess may be 

 mistaken for a new growth and an inflamed aneurism may readily be thought to be 

 an abscess. 



The excision of axillary tumors is difficult. If the tumor is of an inflammatory 

 origin it may be closely adherent to the veins or arteries or nerves, and the same con- 

 dition may exist in malignant cases. 



The blood supply of the axilla is so free that nothing is to be gained by saving 

 small vessels, therefore in paring a tumor off the axillary vessels the various small 

 branches are ligated and divided and the main vessels left bare. This applies to the 

 veins as well as the arteries. 



The subscapular artery is so large that it is often allowed to remain. When 

 working in the posterior portion of the axilla it is to be remembered that the pos- 

 terior circumflex artery is opposite the surgical neck of the humerus, above the 

 tendon of the latissimus dorsi muscle, and that the subscapular artery is on the 

 opposite side of the axillary artery a little higher up. The large subscapular vein 

 will bleed profusely if wounded and it should be looked for at the axillary border of 

 the scapula below the subscapularis muscle. 



Wounds of the axillary vein are particularly dangerous on account of the admis- 

 sion of air. The attachment of the vein to the under side of the pectoralis minor and 

 costocoracoid membrane keeps it from collapsing; hence the danger. 



Nerves of the Axilla. The brachial plexus is above the first portion of the 

 axillary artery. In the second portion one cord is to the inner side, one to the 

 outer, and one behind. In the third portion the median nerve is anterior and a little 

 to the outer side of the artery, being formed by two roots, one from the inner and 

 the other from the outer cord of the brachial plexus. 



The musculocutaneous nerve is to the outer side of the artery, leaving the outer 

 cord to enter the coracobrachialis muscle. The tilnar, internal cutaneous (cutaneus 

 antebrachii medians'}, and lesser internal cutaneous (cutaneus brachii medialis) come 

 from the inner cord and lie to the inner side of the artery. From the posterior cord 

 come the axillary (circumflex) and radial (imisculo spiral) nerves. On the inner wall 

 of the axilla behind the long thoracic artery is the JV. thoracalis longus (long thoracic, 

 or external respiratory nerve of Bell); it is a motor nerve and supplies the serratus 

 anterior (magnus) muscle, hence it is not to be injured in clearing out the axilla. 



Still farther posteriorly, accompanying the subscapular artery, is the thoraco- 

 dorsalis or long subscapular nerve. It also is a motor nerve supplying the latissimus 

 dorsi muscle; therefore it is to be spared. 



Crossing the axilla from the second intercostal space to anastomose with the 

 cutaneus brachii medialis nerve is the inter costobrachial (humeral) nerve. It is a 

 nerve of sensation and need not be spared. Sometimes another branch from the 

 third intercostal nerve also crosses the axilla; it is also sensory and can be cut away. 



As the axillary (circumflex) nerve normally winds around the surgical neck 

 of the humerus, when luxation occurs it is stretched over the head and paralysis of 

 the deltoid may ensue. 



The various nerves of the brachial plexus are often injured by pressure resulting 

 from the use of crutches ("crutch palsy"). It is liable to affect any or several of 

 the nerves, the radial (musculospiral) probably the most frequently. Neuritis is 

 common and, as in injuries, the nerves affected are recognized by the motor or 

 sensory symptoms produced. 



