250 EXPERIMENTAL PHYSIOLOGY. 



elbow joints. The condition has therefore been styled ' REFLEX 

 POSTURAL TONUS ' and it can be shown that the weight required to 

 counterbalance the rigid muscle is practically the same whether 

 muscle is lengthened (knee in extension) or shortened (knee 

 in flexion).* 



If the preparation is still in suitable condition, the experiment 

 should be terminated by exposing the lumbar portion of the spinal 

 cord and cutting the sensory roots of the nerves of the hind limbs 

 What effect has this procedure on the decerebrate rigidity? What 

 conclusions do you draw from the results? 



*The flexor muscles acting on the joint should be paralysed by cutting their 

 nerves in testing these points. 



