1 6 Anatomy Applied to Medicine and Surgery. 



cle are attached to this portion, it is more fixed than the 

 longer, inner portion; (2) it is here that the two curves 

 of the bone meet; (3) because of the change in the form 

 of the bone, whereby the flattened, outer part blends with 

 the cylindrical-shaped, inner portion. For these reasons, 

 then, the direction and force of the vibrations are changed 

 at this point, and the check to their onward course causes, 

 in all probability, an expenditure of energy, which shows 

 itself in the production of a fracture. 



Deformity. The inner fragment is slightly ele- 

 vated by the sterno-mastoid overcoming the combined ac- 

 tions of the clavicular portion of the pectoralis major, the 

 subclavius muscle and the resistance offered by the rhom- 

 boid ligament ; whereas, the outer fragment, and with it 

 the point of the shoulder, is drawn downwards and in- 

 wards and is rotated forwards. It is displaced, downwards, 

 through gravity, assisted by the action (1) of the pector- 

 alis minor on the coracoid process ; (2) of the lower costal 

 portion of the pectoralis major on the humerus, and (3) 

 of the latissimus dorsi on the humerus. Inwards, by the 

 peotoralis major and minor; by the rhomboidei and the 

 levator anguli scapulae; by the middle fibres of the tra- 

 pezius and by the latissimus dorsi. Forward rotation 

 takes place because of the action of the serratus magnus, 

 which, normally, swings the point of the shoulder for- 

 wards through the circumference of a circle, the centre of 

 which is the sterno-clavicular articulation (the radius of 

 the circle being the clavicle) ; hence, if this radius be brok- 

 en, the circle, described by the clavicle, will be less, so that 

 the point of the shoulder moves forward, while the inner 

 portion of the clavicle remains stationary (Fig. 1). ' Frac- 

 tures of the clavicle, dependent on direct injury, are gen- 

 erally transverse, whereas, those due to indirect force are, 

 as a rule, oblique and directed, generally, downwards and 



