Comparisons between Reflex Inhibition and Reflex Excitation 



75 



relaxation from a short series of double shocks at 6000 units delivered 

 at 30 per second. The reaction B was observed one minute after the 

 reaction A, no change 

 having been made in 

 the position of the 

 electrodes, or in the 

 reflex preparation 

 during the interval. 

 From the difference 

 between the two re- 

 flexes it is evident 

 that summation is in 

 marked degree a 

 physiological pro- 

 perty of the reflex 

 arc in its inhibitory 

 as well as in its excitatory reactions. 



II. Some Features of the Reflex 

 Summation. 



It was shown above that in inhibitory re- 

 flexes excited by single induction shocks, the 

 muscle, after elongating, tends, under the con- 

 ditions of experiment, little or not at all to 

 return to the length it had prior to the reflex 

 which relaxed it. The relaxations, therefore, 

 evoked by the individual shocks of a faradic 

 series easily sum. Fig. 8 exhibits the relaxa- 

 tion caused by a make shock and break shock, 

 the latter ensuing somewhat less than one 

 second after the former. The elongation due 

 to the break reflex practically adds itself to 

 that due to the make reflex. This result is 

 not like that which happens under similar 

 circumstances in the excitatory side of the 

 reflex. There a make shock and a break 

 shock following at a second's interval give as 

 result two short reflex contractions, the second 

 not superposed on the height of the flrst, but 

 .starting practically from the same base line as Fig. 7. 



its precursor. The reflex contractions are not 



superposed unless the time interval between the two single stimuli be less 

 than some 150o-.^ With this the inhibitory reflexes stand in apparent 



^ Sherrington, C. S., Integral. Action etc., p. 44. 



