ANIMAL ELECTRICITY. LECTURE I. IJ 



in a nerve and those in the attached muscle, stimu- 

 lating the nerve in the middle of its course, using 

 as indicator of the state of the muscle its me- 

 chanical contraction, and as indicator of the state 

 of the nerve its electrical response. This has been 

 done in the experiment of which fig. 7 is the 

 record. The muscle has been attached to a lever 

 carrying a small paper flag that threw its shadow 

 through a slit upon a photographic plate, which at 

 the same time received the impression of a galvano- 

 metric spot of light moving in obedience to the 

 electrical changes in the nerve itself. The nerve 

 is stimulated once a minute ; the muscle at one end 

 of the nerve contracts, the galvanometer at the 

 other end of the nerve exhibits a negative variation. 

 The pointed shadows of the flag moved by the 

 muscle, give on the developed plate a record of the 

 behaviour of the muscle ; the excursions of the bright 

 spot give a record of the behaviour of the nerve. 

 Now the obvious points are these. By excitation 

 of one and the same nerve there has been a declining 

 series of muscular contractions and a uniform series 

 of negative variations of the nerve-current. The 

 muscle, to all appearance,^ is fatigued, while the nerve 

 exhibits no sign of fatigue. It is thus very clear 

 that muscle does not faithfully express the state of 



^ As will be shown in a future lecture, it is more the nerve- 

 terminal (end-plate) than the muscle that is fatigued ; but this 

 has nothing to do with the present argument. 

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