THE BRACHIAL REGION. 145 



The action of the muscles attached to the humerus upon 

 the fragments in fractures of this bone, are generally as 

 follows : If below the insertion of the muscles attached 

 to the bicipital groove, but above the insertion of the 

 deltoid, this muscle drags the lower fragment upwards 

 and outwards, whilst the former set draw it towards the 

 trunk. If below the insertion of the deltoid, the action 

 of the muscles depends upon the direction of the fracture ; 

 that is to say, whether it be oblique or transverse. 



Bearing in mind that the period of union of the shaft 

 and its epiphysis is about the thirteenth year, we have 

 an important diagnostic point, in cases of difficulty, be- 

 tween fractures immediately above the condyles, sepa- 

 ration of the epiphysis, and dislocation of both radius 

 and ulna backwards. If the fracture exists, the crepita- 

 tion and ready reduction of the bones to their normal 

 position would distinguish it from dislocation. Again, 

 if instead of being transverse, the fracture of the shaft 

 be oblique, in a direction from above downwards and 

 forwards, the triceps will draw the lower fragment up- 

 wards and backwards; if oblique in a contrary direction, 

 the lower fragment would be drawn upwards and for- 

 wards by the brachialis anticus and biceps. 



Owing to the attachment of the flexors and extensors 

 of the wrist and fingers to the condyles, unless the fore- 

 arm be also put up in an angled splint, there is great 

 liability to ununited fracture, as any movement of the 

 wrist would tend to displace or rotate the lower frag- 

 ment. 



