THE ARM. 6 1 



The arm being held up by an assistant, the anterior and 

 posterior borders of the relaxed deltoid admit of being raised 

 so that in amputation at the shoulder the knife can be intro- 

 duced beneath the muscle to make the flap. 



133. Axilla. The anterior border of the axilla, formed 

 by the pectoralis major, follows the line of the fifth rib. In 

 counting the ribs, or in tapping the chest, it is worth remem- 

 bering that the highest visible digitation of the serratus 

 magnus is attached to the sixth rib. The angle of the digita- 

 tion is directed forwards, and corresponds to the upper edge 

 of the rib. The second visible digitation corresponds to the 

 seventh rib ; the interval between these digitations, therefore, 

 corresponds to the sixth intercostal space a convenient place 

 for tapping the chest. (38) 



In the normal state no glands can be felt in the axilla. 



1 34. Axillary artery. When the arm is raised to a right 

 angle with the body, and the head of the humerus thereby 

 depressed, the axillary artery is plainly felt beating, and can be 

 perfectly compressed on the inner side of the coraco-brachialis. 

 This muscle stands out in relief along the humeral side of 

 the axilla, and is the best guide to the artery. A line drawn 

 along its inner border that is, down the middle of the axilla 

 corresponds with the course of the artery. 



The depth and form of the axilla alter in different posi- 

 tions of the arm. In the arm raised and abducted the axilla 

 becomes nearly flat ; hence this position is always adopted in 

 operations. 



In opening abscesses in the axilla, the incision should be 

 made midway between the borders, and the point of the knife 

 introduced from above downwards. 



135. Brachial artery. When the arm is extended and 

 supinated, a line drawn from the deepest part of the middle 

 of the axilla down the inner side of the biceps to the middle 

 of the bend of the elbow, corresponds with the course of the 

 brachial artery. The artery can be felt and compressed all 

 the way down ; but nowhere so effectually as midway, where 

 it lies on the tendon of the coraco-brachialis close to the inner 

 side of the humerus. The only direction to apply the pressure 



