408 Experimental Researches in Cerebral Physiology, [Dec. 10, 



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C. Tracing obtained from the same muscle as in A and B as the result of excitation 

 of the distal end of the cut spinal cord. 



D. Shows the result of rapid excitation of the motor nerve of the same muscle. 



E. Tracing of a voluntary contraction of the opponens pollicis (man). 

 The ordinates indicate seconds, as before. 



nerve-cells in more rapid succession than about ten per second, a 

 process of summation occurs within the nerve-cells, so that the 

 rate of discharge remains about the same in all cases. 3. That the 

 nervous impulses which produce a voluntary contraction also traverse 

 the motor nerve-fibres at about the same rate. There is, however, 

 no distinct evidence to show whether this rhythm of the volitional 

 impulses is generated in the ceils of the cerebral cortex, or in the cells 

 of the lower nerve-centres. 4. That the slower rhythm which is often 

 exhibited in epileptoid contractions is the result of a further summa- 

 tion, but there is no distinct evidence to show where this occurs. 



