THE HUMAN STRUCTURE 93 



The weights needed to produce rupture by flexion and shear- 

 ing, were as follows : 



An effort of torsion acting at the extremity of a lever of 16 

 centimetres, produces a spiral fracture for efforts of the following 

 values : 



Humerus Radius Ulna 

 40 kg. 12 kg. 8 kg. 



Femur Tibia Fibula 

 89 kg. 48 kg. 6 kg. 



The modulus of torsion, or rigidity, on compact bone has not 

 been determined. Theoretically Wertheim gave G = ^ E as an 

 average ( 46). As E 2300, G would equal about 862 ; a value 

 half that of pinewood. 



The following values are of interest : 



kg. 

 1,000 

 ..240 



Lumbar vertebrae com- 1 



pressed vertically J 



Thorax compressed transversely "I 

 (fracture of the ribs). J 



Thorax compressed sagitally. ) 



Man of 30 years 

 Woman of 80 years . 



Man of 30 years ... 200 

 Woman of 82 years ... 40 



Man of 40 years ... 60 

 Woman of 82 years ... 40 



Pelvis crushed, one ridge of the ilium to the other ... 180 

 " Sacrum " crushed sagitally ... 170 to 250 



To sum up, the resistance of the bones increases with age up 

 to the limits of old age, and is more in man than woman, because 

 the osseus tissue of man is denser and his skeleton more massive. 

 The mcde of life and the nature of nutrition modify resistance. 

 This is why the skeleton of a race horse is denser than that of 

 a horse living quietly out at grass. But certain affections attack 

 the bony tissues and decrease their resistance considerably^ 1 ) 



( J ) For the architecture of the skeleton consult H. von Meyer : Die 

 Statik und Mechanik des Menschlichen Knochen-gerustes, Leipzig, 1873. 

 Nevertheless, certain analogies, admitted by the author, are highly doubtful. 



