TIONS). They are of importance in this connection from a negative point of view: because, like fractures of the skull, their relation to injury of the tained viscera is by no means constant.
The significance of fracture of the the usual osseous lesion—is commonly overestimated. A surprisingly small percentage of those whose ribs are broken suffer any visceral injury, while an astonishingly large proportion of those who suffer more or less serious, even fatal, rupture of the lungs or heart show no lesion of the thoracic cage ever. Thus, among Fischer's 76 cases of rupture of the heart, 32 showed no evi dence of fracture. The explanation of this apparent paradox lies in the great elasticity of the thorax, especially in the young (it decreases with advancing age).
Weisserer claims that up to the age of twenty-five the sternum can be pressed back to touch the vertebral column out injury to the ribs. Thus in the young, in those, namely, who are posed to the greatest number of injuries, the force is transmitted through the bones to the viscera, while in the adult and aged the bones are more likely to break.
An interesting comparison has been personally made between man and other animals in respect to the shape of the thorax in determining the effect of direct and indirect force in producing fractures of the ribs. The conclusion is that the
lesser curve of the ribs with increased strength in quadrupeds is a factor of safety greater than the greater curve and increased elasticity in man. Still, the ribs of quadrupeds may be broken by both direct and indirect violence, while in man indirect force more often leads to fracture, the ribs only being driven in at the place struck, the fracture occur ring a little way off. It is thought that this explains the comparative absence of injuries to the deeper-lying structures, such as would naturally be expected to occur, from direct violence. E. M. Cor ner (Lancet, Jan. 7, '99).
Yet it cannot be denied that a frag ment of bone, whether detached or only momentarily depressed, is often the im mediate cause of visceral rupture. But these cases differ clinically in no way from those in which there is no fracture, excepting rupture of the pleura.