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Applied Biophysics 



in almost every accident, the linear acceleration, (ci), can be 

 neglected in comparison with the rotational acceleration, (co). 

 There is an essential difference between linear and rotational 

 movement. When the skull is moved in a straight line, it is the 

 brain's incompressibility which prevents it from being left behind. 

 This being very high, none of it lags behind, so that it moves as 

 a whole, and there is no appreciable distortion ( figure 1 ) . On the 

 other hand, when the skull is rotated, the brain has to depend 

 on its rigidity to avoid being left behind. But its rigidity is small, 

 so that parts of it do get left behind to a considerable degree. 

 It is therefore distorted (figures 3 and 4). 



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FIG. 3. Absolute movement in space of a skull and real brain of small rigidity 

 when the skull is rotated about o. Arrows as in figures 1 and 2. Skull and brain 

 do not rotate together as a single rigid unit. The brain moves relative to the skull 

 and is therefore distorted and injured. 



