240 Prof. C. S. Sherrington. Nervous Rhythm [Feb. 3, 



excitation ; examples, it is true, in which the regularity and amplitude 

 of rhythmic contraction and relaxation have reached their full. That these 

 rhythmic contractions are really analogous to the simple undulatory reflex 

 contractions cited and discussed above seems clear from several considerations. 

 (1) Both occur under the same circumstance, namely, concurrence of 

 inhibition and excitation. (2) Both exhibit the same rate of rhythm. 

 (3) It has not been difficult in my experiments to find intermediate examples 

 connecting the more developed forms with the less developed. Thus, the 

 example fig. 2 is intermediate between the form exhibited by fig. 1, and the 

 example figured in observation A, fig. 6 ; and the example fig. 3 seems 

 to me intermediate between that of fig. 1 and the example figured by Forbes 



Pig. 3. — Eeflex reciprocal stepping of isolated extensor muscle of knees, right and left, 

 evoked by concurrent stimulation of the antagonistic afferents r.p., right peroneal, and 

 l.p., left peroneal. Decerebrate cat. R.V., right vastocrureus muscle ; L.V., left 

 fellow muscle. Time above in fifths of seconds. In addition to the rhythmic 

 stepping, which is here somewhat rapid, there is a minute tremor of much more rapid 

 rate (see text) engrafted on and disturbing the stepping reflex's rhythm. 



