chap. XL] THE CLAVICLE. 193 



accidents, this connection being broken through, it is 

 possible for the extremity to be torn off entire. Thus 

 Billroth reports the case of a boy aged fourteen, 

 whose right arm, with the scapula and clavicle, was so 

 torn from the trunk by a machine accident, that it was 

 only attached by a strip of skin two inches wide. Other 

 like cases of avulsion of the limb have been reported. 

 Fractures of clavicle. The clavicle is more 

 frequently broken than is any other single bone in 

 the body. This frequency is explained by the fact 

 that the bone is very superficial, is in a part exposed 

 to injury, is slender and contains much compact 

 tissue, is ossified at a very early period of life, and 

 above all receives a large part of all shocks communi- 

 cated to the upper extremity. The common fracture, 

 that due to indirect violence, is oblique, and very 

 constant in its position, viz. at the outer end of the 

 middle third of the bone. The bone breaks at this 

 spot for the following reasons. It is here that the 

 clavicle is the most slender ; it is here that the 

 two curves of the bone meet ; it is here that a very 

 fixed part of the bone, viz. the outer third, joins 

 with a more movable portion. The position of the 

 coraco-clavicular ligaments is no doubt of the greatest 

 import in localising the fracture in this position, since 

 a clavicle experimentally subjected to longitudinal 

 compression does not break at this spot (Bennett). 

 The displacement that occurs is as follows. The inner 

 fragment remains unchanged in position, or its outer 

 end is drawn a little upwards by the sterno-mastoid. 

 It will be seen that any action of this muscle would 

 he resisted by the pectoralis major and the rhomboid 

 ligament. The outer fragment undergoes a threefold 

 displacement. (1) It is carried directly downwards. 

 This is effected mainly by the weight of the limb 

 aided by the pectoralis minor, the lower fibres of the 

 pectoralis major, and the latissimus dorsi. Since the 



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