PLATE I. 



THE AXILLA, SUPERFICIAL VIEW. 



The cutaneous nerves which supply the front 

 of thorax and upper arm are indicated by black 

 lines in the accompanying diagram, viz. : 

 (a) Sternal, (b) clavicular, (c) acromial branches 

 from the cervical plexus (8 and 4 c) ; (d) anterior, 

 and (e) lateral cutaneous branches of the inter- 

 costala ; (/) branches from circumflex ; (g) upper 

 branches of the internal cutaneous. The position 

 of the bones is shown in faint outline. 



The AXILLA is a pyramidal space with the 

 base directed downwards and outwards, and covered 

 in by dense fascia ; and the apex directed upwards 

 and inwards between the clavicle and first rib. 

 The boundaries are : 



In front : Pectoralis major and minor, costo-coracoid membrane, and subclavius 

 muscle. 



Behind : Subscapularis, latissimus dorsi, and teres major muscles. 

 Externally : Coraco-brachialis and biceps muscles, and humerus. 



Internally : About five ribs, their intcrcostals, and five serrations of serratua 

 magnus. 



It contains the axillary vessels and brachial plexus of nerves running along its outer 

 wall, with their branches. Lymphatic glands : one set along the line of the vessels 

 receiving the lymph from the arm ; another along the edge of the pectoralis major, receiving 

 the lymph from the breast and front of thorax ; and a third set along the line of the 

 subscapular vessels, receiving the lymph from the back of thorax. There are also 

 lateral branches of the intercostal nerves, and the space is filled with a packing of fat. 



The intercosto-humeral nerve, the lateral cutaneous branch of the second inter- 

 costal nerve, usually sends a branch to join the nerve of Wrisberg ; but if the latter is 

 larger than usual, it will in turn give off one to join the intercosto-humeral, as in 

 the plate. 



The first intercostal nerve usually sends no lateral cutaneous branch, but it is 

 occasionally present (vide Plate III.) and then generally joins the nerve of Wrisberg, 

 giving a twig to join the intercosto-humeral. 



The nerve-twig marked (7) is a special branch of the musculo-spiral to the lower 

 fibres of the internal head of the triceps, and from its course parallel to, and being 

 sometimes bound up with, the ulnar nerve, it is called the ulnar collateral. 



The posterior or long thoracic is also known as the external respiratory nerva 

 of Bell. 



