THE ARM. 59 



THE ARM. 



130. Clavicle The line of the clavicle and the projection 

 of the joint at either end of it can always be felt, even in the 

 fattest persons. Its direction is not perfectly horizontal, but 

 slightly inclined downwards, when the arm hangs quietly by 

 the side. When the body lies flat on the back, the shoulder 

 not only falls back, but rises a little, the weight of the limb 

 being taken off. Hence the modern practice of treating 

 fractures of the clavicle (in the early stage) by the supine 

 position. 



On the front surface of the clavicle, not far from its 

 acromial end, there is in many persons of mature age a 

 spine-like projection of bone. So far as I know, it has not 

 been described. A gentleman, himself a surgeon, showed 

 me an instance in his own person. He suspected it was an 

 exostosis. 



As a rule the acromio-clavicular joint forms an even 

 plane. But there is sometimes a knob of bone at the acromial 

 end of the clavicle ; or it may be only a thickening of the 

 fibro-cartilage, sometimes .existing in the joint. In either 

 case this relief might be mistaken for a dislocation, or even 

 for a fracture. A reference to the other shoulder might settle 

 the question. 



131. Bony points of the shoulder. We can distinctly 

 feel the spine of the scapula and the acromion, more especially 

 at the angle where they join behind the shoulder. This angle 

 is the best place from which to measure in taking the com- 

 parative length of the arms. 



In some shoulders, though very rarely, there is an ab- 

 normal symphysis between the spine of the scapula and the 

 acromion. There may indeed be two symphyses and two 

 acromial bones, the acromion having two centres of ossifica- 

 tion. These abnormal symphyses might be mistaken for 

 fractures, until we have examined the opposite shoulder, 

 which is sure to present a similar conformation. 9 



Tuberosities. Projecting beyond the acromion (the arm 

 hanging by the side), we can feel, through the fibres of the 



