80 



Applied Biophysics 



FIG. 5. The shear strains (= distortion) which arise when a gelatin model is 

 rotated as in figure 3, or in the reverse direction. The darker the shading the greater 

 the distortion. Note the comparative absence of distortion in the lateral cerebellar 

 lobe and high distortion at tip of the temporal lobe. 



hold for glass or metal. Figure 5 refers only to blows of long 

 duration. 



Rotation causes the so-called contrecoup injuries, and presum- 

 ably (as the effects of fracture and skull bending are purely 

 local) concussion. It follows that if the head can only rotate 

 slowly, e.g., in the case of crushing between railway buffers, 

 or is fixed, there is no concussion. The latter result agrees with 

 that of Denny-Brown and Russell,^ but not with that of Scott. ^^ 

 From a well-known theorem in kinematics, it makes absolutely 

 no difference to the rotational component of injury whether the 

 rotation is one about an axis through the "center" of the brain, 

 or is an equal one about a parallel axis through the atlas or 

 through Timbuktoo. But since the last case would involve a 

 linear acceleration up to millions of miles per hour, the rotational 

 component of injury would be comparatively unimportant. The 

 rotational injury is ai)proximately the same whether the head 

 rotates forward from a blow on the occiput, or backward from 



