Flexor-rejiex evoked by a Single Break-shock. 



117 



motor nerve excites there not a repetitive series of impulses but (per fibre) 

 one single impulse only, evoking a twitch contraction, not in a tetanic 

 contraction. 



On the other hand, it may be that the spinal reflex centre on receipt of a 

 single-impulse volley from the afferent nerve responds by an impulse- 

 discharge repetitive in character. Such a result might be due to the impinge- 

 ment upon the centre's cells severally of numbers of terminals coming from 

 the afferent path, so that upon any one central neurone there converged a 

 number of excitatory impulses, some arriving later than others. Or it may 

 be that across the central path of the reflex there is some structure, e.g., a 

 synaptic membrane, which has a property of repetitive activity in result of, or 

 in response to, the arrival at it of even a single impulse or of a single 

 simultaneous set of impulses. 



EEFEEENCES. 



1. Asayama, C, ' Quart. J ourn. of Physiol.,' vol. 9, p. 265 (1916). 



2. Dreyer, N. B., and Slierrington,^_C. S., ' Eoy. Soc. Proc.,' B, vol. 90, p. 270 (1918). 



3. Forbes, A., and Gregg, A., ' Amer. Journ. Physiol.,' vol. 37, p. 118 (1915), and vol. 39, 



pp. 172, 491 (1915). 



4. Ishikawa, H., ' Zeitschr. Allg. Physiol.,' vol. 11, p. 150 (1910). 



5. Sherrington, C. S., ' Phil. Trans.,' B, vol. 190, p. 98 (1898). 



6. Sherrington, C. S., 'Journ. of Physiol.,' vol. 40, p. 105 (1910). 



7. Sherrington, C. S., and Sowton, S. C. M., 'Journ. of Physiol.,' vol. 49, p. 331 (1916). 



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