THE FOKE-BKAIN 



569 



therefore seem to be, at all events for this form of inhibition, 

 distinct paths for motor and for inhibitory impulses. 



Among the most classical examples of this so-called reciprocal 

 innervation of the antagonist muscles, is that which Sherriugton 

 discovered for the muscles of the eye-ball. If in the cat or 

 monkey the oculo-rnotor and the trochlear nerves of the left side 

 are cut so that only one muscle, the external rectal, remains active 

 in the eye of this side, and the area in the frontal or the occipital 

 lobe which normally produces conjugate movements of both eyes 

 to the right (Fig. 281) is then faradised, there will lie a deviation 

 to the right not only of the normal right eye owing to the con- 

 traction of the right external rectus, but also of the paralysed 



FIG. 291. Weaker inhibitory effect after faradising the pie-frontal lobe on same side as the ga.stru- 

 cnemius that is making the tracing. (Oddi.) The three lines correspond to those of the previous 

 figure. 



left eye owing to relaxation of the left external rectus. By a 

 similar experiment, after section of the sixth abducens nerve, an 

 inliibitory action on the right internal muscle of the operated 

 eye can be demonstrated, associated with contraction of the 

 internal rectus of the normal eye. 



Another example of reciprocal innervation may be seen in the 

 extensor and flexor muscles of the extremities. In chloroform 

 and ether narcosis there is a stage during which a state of flexion 

 or tonic extension of the extremities can be observed. If in a 

 monkey in this state the cortical areas which determine the con- 

 traction of the flexors are faradised, relaxation of the extensors 

 can lie distinctly perceived if the muscles are felt with the hand. 

 If the cortical areas of the extensors are faradised, while the flexor 

 muscles are held in the hand, relaxation of these muscles can be 

 distinctly felt. 



