596 SCIENCE PROGRESS 



is that it produces an effect on the antagonistic muscles re- 

 sembling one that, as said above, is often observable in voluntary 

 actions. The inference is that in these willed actions the 



Fig. 4. — Reflex contraction of Semitendinosus, Fl, and Vastocrureus, Et, recorded 

 with double-myograph. 



The lever attached to vastocrureus (,£{), writes not directly below but about a centimetre to the right of 

 that attached to semitendinosus (/'V) ; control arcs, cut when the recording surface was not moving, 

 indicate the amount of commencement of stimulus on each myogram line. The ipselateral peroneal 

 nerve (afferent end) is stimulated as shown by the lower signal line Fl! , and causes contraction of semi- 

 tendinosus and relaxation of vastocrureus. Then follows stimulation of contralateral peroneal nerve as 

 shown by the upper signal Et' . This combined stimulation lessens, but not to extinction, the 

 contraction of semitendinosus and at the same time brings into contraction the antagonistic muscle, 

 vastocrureus. On reverting to the single stimulation again, the contraction of semitendinosus increases 

 once more and that of vastocrureus disappears. Finally, on cessation of the single stimulation Ft , a 

 rebound, r, from inhibitory relaxation to increased tonic contraction occurs in vastocrureus synchronously 

 with the relaxation of the flexor. Time above in seconds. Decerebrate cat. 



cerebral centres have the power of employing simultaneously 

 the play of two or more opposed influences upon the motor 

 centres. In other words, in these willed actions the grading of 



