150 SURGICAL APPLIED ANATOMY. [Chap. x. 



If a horizontal line be drawn round the body at the 

 level of the inferior angle of the scapula, while the 

 arms are at the side, the line would cut the sternum 

 in front between the attachments of the fourth and 

 fifth ribs, would cut the fifth rib at the nipple line, 

 and the ninth rib at the vertebral column. The 

 second rib is indicated by the transverse ridge on the 

 sternum already alluded to. The lower border of the 

 pectoralis major leads to the fifth rib, and the first 

 visible serration of the serratus magnus corresponds to 

 the sixth. The longest rib is the seventh, the shortest 

 the first. Tn breadth the bones decrease from the first 

 to the twelfth. The most oblique rib is the ninth. 



The ribs are elastic and much curved, and being 

 attached by many ligaments behind to the column, 

 and in front to the yielding cartilages, resist injuries 

 tending to produce fracture with the qualities 

 possessed by a spring. A rib may be fractured by 

 indirect violence, as by a wheel passing over the body 

 when lying prostrate on the back. In such a case 

 the force tends to approximate the two ends of the 

 bone, and to increase its curve. When it breaks, 

 therefore, it breaks at the summit of its principal 

 curve, i.e., about the centre of the bone. The 

 fragments fracture outwards, and the pleura stands 

 no risk of being penetrated. When the rib is broken 

 by direct violence, the lesion occurs at the spot 

 encountered by the force, the bone fractures inwards, 

 the curve of the rib tends to be diminished rather than 

 increased, and there is much risk of the fragments 

 lacerating the pleura. 



Those most often broken are the sixth, seventh, 

 and eighth, they being under ordinary circumstances 

 the most exposed. The rib least frequently fractured 

 is the first, which lies under cover of the clavicle. 

 Fractures are more common in the elderly than in 

 children, owing to the ossification of the cartilages 



