SOME RECENT WORK UPON MUSCLE AND NERVE. 443 



ing the column by means of a microscope upon a travelling 

 photographic plate. In nerve the difficulty lies in the cir- 

 cumstance that the movement produced by nerve electrical 

 changes must under all conditions be extremely small in 

 extent, and that in addition to this it is of very short dura- 

 tion. It is thus impossible to follow it with the eye even 

 when the magnified image of the mercurial column is so 

 enlarged by projection as to be 400 times the size of the 

 object. If, however, the plate is travelling with sufficient 

 velocity the moving shadow thrown by the enlarged image, 

 although too transient to be perceptible to vision, is found 

 to have occurred when the plate is developed. In this way 

 records have been obtained of the electrical disturbance 

 evolved in nerve by each single stimulus, and convincing 

 proof is afforded that this single electrical response, starting 

 from the seat of stimulation, is successively assumed by 

 each more distant portion of a continuous nerve tract. The 

 method has the distinction of being the only one by which up 

 to the present the single change has been recorded. A large 

 number of experiments have been made with nerves under 

 different conditions, and the modifications in the response 

 consequent upon these have been recorded. We have here 

 the start of an inquiry which will, it is hoped, effect for 

 nerve what the graphic record has done for muscle, since 

 each record is a graphic account of the nerve change as 

 given by such an historian as the electrometer. Is the 

 electrometer a reliable historian or has it a large personal 

 bias ? This question admits of much discussion, and has 

 been taken up ad\ ersely by several of the leading German 

 physiologists, particularly Hermann. 



Without entering into the somewhat technical contro- 

 versy, this much may be stated here. Each electrometer 

 has its own rate of movement, its own personal equation ; 

 every record has therefore to be interpreted afresh after 

 making due allowance for this personal bias of the instru- 

 ment. Fortunately the amount and character of the bias 

 remains approximately constant for any one instrument, so 

 that if it can be determined the allowance is easily made for 

 all records obtained from the particular instrument whose 



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