Chap, xi.] THE CLAVICLE. 169 



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. Tho 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 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 be resisted 

 by the pectoralis major, and the rhomboid ligament. 

 The outer fragment undergoes a threefold displace- 

 ment. (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. (2) It is carried 

 directly inwards by the muscles tha.t pass from the 

 trunk to the shoulder, viz., the trapezius, the levator 

 anguli scapulae, the rhomboids, the latissimus dorsi, and 

 especially by the pectorals. To these may be added 



