Chap, x.) THE THORAX. 173 



the sixth to the tenth, and the seventh to the eleventh. 

 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 at the attachment of the sixth cartilage, would 

 cut the fifth rib at the nipple line, and the eighth 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. In 

 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 en- 

 countered 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 



