616 Professor C. S. Sherrington [April 19, 



duced from simple dissection of the musculatm-e of the dead limb. 

 Experiment with the living limb teaches that natm*e does not expend 

 her muscular energy in using the power of one muscle to simply 

 curb the power of another. When the knee is bent the reflex act does 

 not hamper the working of the flexor muscles by causing a contraction 

 of the extensors also. Nor does it simply leave the extensors out of 

 account. No ; it causes them to relax and lengthen at the same time 

 as it causes the flexor muscles to contract and shorten. This it 

 does by reflex inhibition. And it proportions the grade of this re- 

 laxation exactly to the grade of contraction of the opponent muscles. 

 The inhibition acts, not on the muscle directly, but on the motor 

 nerve-cells innervating the muscle. These nerve-cells are long fila- 

 ments ; one end of each lies in the muscle the other in the spinal cord. 

 The reflex inhibition is exercised upon them at the end which lies in 

 the spinal cord. In the reflex we are considering, the reflex action 

 besides exciting the motor nerve-cells of the three muscle groups — 

 flexors, abductors, and internal rotators — before mentioned, inhibits 

 the motor nerve-cells of three muscle groups antagonistic to those, 

 namely the extensors, the abductors, and external rotators. "We see, 

 therefore, that in even the simple reflex lifting of the foot, almost 

 every one of the many muscles composing the whole musculature of 

 the limb receives from the nervous system a controlling influence, 

 either of excitation to contract or of inhibition which relaxes con- 

 traction. And all this in result of a simple touch of the skin of the 

 foot. The reaction typifies in a simple manner the action of the 

 nervous system to knit the heterogeneous powers of the body together 

 into one harmonious whole. 



Thus we see that in these actions when one group of muscles 

 contracts, the group antagonistic to it relaxes. This is a fundamental 

 part of the co-ordination of the act, and its discovery throws a welcome 

 light on the nature of certain maladies. W^ere the antagonistic 

 group to contract at the same time as the protagonist, the desired 

 movement would not result. The movement which then ensued 

 would depend on which of the two muscle groups were the stronger, 

 the protagonist or the antagonist. The alkaloid strychnine and the 

 poison produced by the bacilli which cause the malady called " lock- 

 jaw " possess the power of destroying reflex inhibition. What the 

 intricate nature of the process of this inhibition is we do not yet 

 know, but it seems to be the exact converse of the process of excita- 

 tion, whose nature is also unknown. Strychnine and tetanus-toxin 

 change the process of inhibition into its converse namely excitation. 

 If a minute dose of strychnine be administered, the reflex which as 

 we saw causes the limb to bend, now causes the limb to straighten 

 instead. This is because the extensors, when the flexors contract, 

 instead of being relaxed by inhibition are excited to contraction, and 

 being more powerful than the flexors, move the limb in exactly the 

 opposite direction to that in which it should move in this reflex action. 



