THE AXILLARY ARTERY. 589 



size, and numerous lymphatic glands : these are from ten to twelve in number, and 

 situated chiefly on the thoracic side and lower and back part of this space. 



Surgical Anatomy. The axilla is a space of considerable surgical importance. It trans- 

 mits the large vessels and nerves to the upper extremity, and these may be the seat of injury or 

 disease : it contains numerous lymphatic glands which may require removal when diseased ; in it 

 is a quantity of loose connective and adipose tissue which may be readily infiltrated with blood 

 or inflammatory exudation, and it may be the seat of rapidly-growing tumors. Moreover, it is 

 covered at its base by thin skin, largely supplied with sebaceous and sweat glands, which is fre- 

 quently the seat of small cutaneous abscesses and boils, and of eruptions due to irritation. 



In suppuration in the axilla the arrangement of the fasciae plays a very important part in the 

 direction which the pus takes. As described on page 468, the costo-coracoid membrane, after 

 covering in the space between the clavicle and the upper border of the Peetoralis minor, splits 

 to enclose this muscle, and. reblending at its lower border, becomes incorporated with the fascia 

 covering the Peetoralis major muscle at the anterior fold of the axilla. This is known as the 

 clavi-pectoral fascia. Suppuration may take place either superficial to or beneath this layer of 

 fascia : that is. either between the pectorals or below the pectoralis minor : in the former case, 

 it would point either at the anterior border of the axillary fold or in the groove between the Del- 

 toid and the Pectoralis major ; in the latter, the pus would have a tendency to surround the vessels 

 and nerves and ascend into the neck, that being the direction in which there is least resistance. 

 Its progress toward the skin is prevented by the axillary fascia ; its progress backward, by the 

 Serratus magnus ; forward, by the clavi-pectoral fascia ; inward, by the wall of the thorax ; and 

 outward, by the upper limb. The pus in these cases, after extending into the neck, has been 

 known to spread through the superior opening of the thorax into the mediastinum. 



In opening an axillary abscess the knife should be entered in the floor of the axilla, midway 

 between the anterior and posterior margins and near the thoracic side of the space. It is well 

 to use a director and dressing forceps after an incision has been made through the skin and fascia 

 in the manner directed by the late Mr. Hilton. 



The student should attentively consider the relation of the vessels and nerves in the several 

 parts of the axilla, for it not unfrequently happens that the surgeon is called upon to extirpate 

 diseased glands or to remove a tumor from this situation. In performing such an operation it 

 will be necessary to proceed with much caution in the direction of the outer wall and apex of the 

 spun-, as here the axillary vessels will be in danger of being wounded. Toward the posterior wall 

 it will be necessary to avoid the subscapular, dorsalis scapulas, and posterior circumflex vessels. 

 All HI 2 the anterior wall it \\i\\ be necessary to avoid the thoracic branches. It is only along the 

 inner or thoracic wall, and in the centre of the axillary cavity, that there are no vessels of any 

 importance a fortunate circumstance, for it is in this situation more especially that tumors 

 requiring removal are usually situated. 



THE AXILLARY ARTERY. 



The Axillary Artery, the continuation of the subclavian, commences at the 

 lower border of the first rib, and terminates at the lower border of the tendon of 

 the Teres major muscle, where it takes the name of brachial. Its direction varies 

 with the position of the limb : when the arm lies by the side of the chest, the 

 vessel forms a gentle curve, the convexity being upward and outward ; when it is 

 directed at right angles with the trunk, the vessel is nearly straight ; and when 

 it is elevated still higher, the artery describes a curve the concavity of which is 

 directed upward. At its commencement the artery is very deeply situated, but 

 near its termination is superficial, being covered only by the skin and fascia. The 

 description of the relations of this vessel is facilitated by its division into three 

 portions, the first portion being that above the Pectoralis minor ; the second por- 

 tion, behind ; and the third below, that muscle. 



The first portion of the axillary artery is in relation, in front, with the clavic- 

 ular portion of the Pectoralis major, the costo-coracoid membrane, the external 

 anterior thoracic nerve, and the acromio-thoracic and cephalic veins ; behind, with 

 the first intercostal space, the corresponding Intercostal muscle, the second and 

 third serrations of the Serratus magnus, and the posterior thoracic nerve ; on its 

 outer side, with the brachial plexus, from which it is separated by a little cellular 

 interval ; on its inner or thoracic side, with the axillary vein. 



KELATIONS OF THE FIRST PORTION OF THE AXILLARY ARTERY. 



In front. 

 Pectoralis major. 

 Costo-coracoid membrane. 

 External anterior thoracic nerve. 

 Acromio-thoracic and Cephalic veins. 



