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PRINCIPLES OF GENERAL PHYSIOLOGY 



nerve is first stimulated and the muscle is released from the tonic excitation of 

 the centre. In the middle of this period of stimulation, the exciting nerve is 

 stimulated, the inhibition of the centre is almost neutralised, so that the muscle 

 returns nearly to its original length. While this stimulation is continued, the 



BALANCE OF REFLEX EXCITATION AND INHIBITION IN THE CASE OF 

 SKELF.TAL MUSCLE (VASTO-CRFKKIs). 



In the left-hand tracing (A) the myogram (m) shows that medium (decerebrate) tonus is present at the 

 commencement. The fall of the signal line / indicates that the central end of an inhibitory 

 afferent nerve, the iiwelateral peroneal, is excited by 1W) units of the coil graduation. The level 

 falls. It is brought back again nearly to its original height by concurrent stimulation (shown by 

 signal K) of an excitatory nerve, contralateral popliteal, with MX) units. When the inhibitorx 

 stimulus is cut off, the full effect of the excitatory one shows itself. 



In the right-hand tracing (B) the order in which the two nerves are stimulated is reversed. 



Note the greater rapidity of the flnal fall in B than in A. This is due to the fact that in B it is 

 produced by active inhibition, in A by mere cessation of excitation. 



(Sherrington, 1908, Fig. 4.) 



inhibiting stimulus is removed, with the result that the exciting stimulus can 

 produce its full effect unhindered. In B, the converse experiment is performed, 

 commencing with the stimulation of the exciting nerve. Sherrington concludes 

 that the eftect is a simple algebraic summation of the two single effects (see also 



