THE AXILLARY FOSSA 



1411 



owing to the presence of fibrous septa continuous, alike, with the skin and the sheath of the 

 muscle and the tendinous septa which separate the muscular bundles, will also be seen. The 

 muscle will be marked out by a base-line reaching along the above bony points, and two sides 

 converging from its extremities to the apex, a point on the lateral surface of the humerus, about 

 its centre. In paralysis of the deltoid, the humerus being no longer braced up against the 

 scapula, the finger-tips can be placed between it and the acromion. 



To map out the pectoralis major, a line should be drawn down the lateral aspect of the 

 sternum as far as the sixth costal cartilage, and then two others marking the borders of the 

 muscle — the upper corresponding to the medial border of the deltoid, the lower starting from 

 the sixth cartilage, and the two converging to the folded tendon, which is inserted as a double 



Fig. 1129. — The Shoulder-joint, as shown by the Rontgen-rays. 



layer into the lateral tubercular (bicipital) ridge. The pectoralis minor will be marked out by 

 two lines, from the upper border of the third and the lower border of the fifth rib, just lateral 

 to their cartilages, and meeting at the coracoid process. The lower line gives the level of the 

 long thoracic artery; the upper, where it meets the line of the axillary artery, that of the thoraco- 

 acromial. 



When the arm is abducted and the humerus rotated a little laterally, the prominence of a 

 well-developed coraco-brachialis comes into view; a line drawn from the centre of the clavicle 

 along the medial border of this muscle to its insertion into the humerus gives the line of the 

 axillary artery. 



Axillary fossa. — The boundaries of this space anterior, posterior, medial, or 

 thoracic, lateral or humeral, apex and base, with the structures forming them and 



