256 A MANUAL OF ANATOMY. 



to join the acromion process of the scapula, and thus hinge 

 the upper extremity to the thorax. 



The articulation between the clavicle and the acromion is 

 usually easily found, and often is so prominent as to consti- 

 tute almost a subluxation of the former upon the latter. 

 The margin of the acromion can be traced, and the angle 

 formed by the junction of the spine with the acromion is 

 always easily located. This point is the one from which 

 measurements are made in determining differences in the 

 length of the upper extremity. The lower fixed points 

 depend upon the part to be measured. If only the arm, 

 the external condyle of the humerus or the tip of the olec- 

 ranon with the forearm flexed to a right angle. For the 

 arm and forearm, the tape is carried to the tip of the styloid 

 process of the radius or ulna, and for the entire extremity, 

 to the point of the middle finger (any finger or point will 

 do provided the corresponding point is taken on the opposite 

 side of the body). 



In front of the middle and outer thirds of the clavicle is 

 usually a depression corresponding to the interval between 

 the pectoralis major and deltoid muscles ; in this depression 

 the tip of the coracoid process will be found by making a 

 little pressure. 



The cephalic vein lies in the groove between the deltoid 

 and pectoralis major muscles and passes upward to empty 

 into the axillary vein below the middle of the clavicle. 



The deltoid tubercle may be prominent enough to be dis- 

 cerned by touch at the outer and middle thirds of the anterior 

 border of the bone. Under the deltoid muscle the tuber- 

 osities of the humerus can be felt, especially on rotation 

 of the bone. The greater is external, the lesser internal, 

 and between them is the bicipital groove, which can be 

 appreciated in thin people. 



