1912.] Innervation and Symmetrical Muscles. 229 



strong contralateral stimulus to an already existent ipsilateral has increased 

 instead of lessened the contraction (fig. 9), and this has been so not only 

 during the application of the contralateral stimulus but still further on its 

 withdrawal. A rebound contraction of the flexor muscle has then occurred, 



Fig. 9. — Psoas and sartorius muscles, flexors, of right and left limbs. Stimulation of 

 right peroneal with a weak stimulus, coil at 24 cm. from primary ; during this 

 stimulation the left peroneal is stimulated for about one second with a strong 

 stimulus, coil at 14 cm. from primary. The contraction of right flexors is increased 

 during stimulation of left nerve, and on cessation of this stimulation a still further 

 rebound augmentation of the right muscle's contraction occurs. Decerebrate cat. 



adding itself to the contraction due to ipsilateral nerve, and causing a combined 

 contraction of large amplitude. 



It is obvious that such reactions though outside the main principle above 

 stated work in the direction of assisting a double reciprocal innervation to 

 change the reflex effect on the symmetrical muscles from reciprocal to identical 

 character. The contraction of both flexors will be increased and so also the 

 inhibitory relaxation of both extensors. 



