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THE BLOOD-VASCULAR SYSTEM. 



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 a 

 portion of the third digitations of the Serratus magnus, and the posterior thoracic 

 and internal anterior thoracic nerves ; 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, which overlaps the artery. 



RELATIONS OF THE FIRST PORTION OF THE AXILLARY ARTERY. 



In front. 

 Pectoralis major. 

 Costo-coracoid membrane. 

 External anterior thoracic nerve. 

 Acromio-thoracic and Cephalic veins. 



Outer side. 

 Brachial plexus. 



Inner side. 

 Axillary vein. 



Behind. 



First Intercostal space and Intercostal muscle. 

 Second and third digitations of Serratus magnus. 

 Posterior thoracic and Internal anterior thoracic nerves. 



The second portion of the axillary artery lies behind the Pectoralis minor. It 

 is covered, in front, by the Pectoralis major and minor muscles; behind, it is 

 separated from the Subscapularis by a cellular interval ; on the inner side is the 

 axillary vein, separated from the artery by the inner cord of the plexus and the 

 internal anterior thoracic nerve. The brachial plexus of nerves surrounds the 

 artery on three sides, and separates it from direct contact with the vein and adjacent 

 muscles. 



RELATIONS OF THE SECOND PORTION OF THE AXILLARY ARTERY. 



In front. 

 Pectoralis major and minor. 



Outer side. 

 Outer cord of plexus. 



Inner side. 



Axillary vein. 



Inner cord of plexus. 



Internal anterior thoracic nerve. 



Behind. 

 Subscapularis. 

 Posterior cord of plexus. 



The third portion of the axillary artery lies below the Pectoralis minor. It is 

 in relation, in front, with the lower part of the Pectoralis major above, being 

 covered only by the integument and fascia below, where it is crossed by the inner 

 head of the median nerve ; behind, with the lower part of the Subscapularis and 

 the tendons of the Latissimus dorsi and Teres major; on its outer side, with the 

 Coraco-brachialis ; on its inner or thoracic side, with the axillary vein. The nerves 

 of the brachial plexus bear the following relation to the artery in this part of its 

 course : on the outer side is the median nerve, and the musculo-cutaneous for a 

 short distance ; on the inner side, the ulnar (between the vein and artery) and 

 lesser internal cutaneous nerves (to the inner side of the vein) ; in front, is the 



