PHENOMENA OF MUSCLE AND NERVE. 305 



formerly viewed with distrust) and with very short durations of 

 closure. Finally, the investigation had also to be extended to the 

 case of muscle. 



The method of experiment was that described previously in this 

 communication, the leading-off electrodes being now extrapolar. 

 The insulation of the two circuits by means of a paraffin commuta- 

 tor proved quite effectual also for these experiments, although, as I 

 knew from previous work, the disturbing effect of bad insulation is 

 more marked in the case of extrapolar than in that of intrapolar 

 experiments. This latter circumstance is easily explained ; for if the 

 material of the commutator is at all conductive, then, during the 

 closure of the battery circuit, derived currents will pass through the 

 galvanometer which, in the case of extrapolar leading-off, must, 

 however derived, be similarly directed through the instrument, 

 whereas in the case of intrapolar leading-off these would be opposed 

 in direction, and consequently would in part compensate each other ; 

 in this last case it is as though the galvanometer was introduced 

 into the cross wire of a Wheatstone's bridge. 



A large number of experiments, with currents of from i to 1 8 

 zinc carbon elements and of durations of closure from I to 60 

 seconds, establish the following propositions. 



The deflection is in the case of nerve always in accordance with 

 my previous observations ; that is, on the side of the kathode it is 

 + } similar in direction to the previous polarising current ; on the 

 side of the anode it is , opposed in direction to the previous 

 polarising current ; in other words, it is, in both situations, directed 

 away from the led-through portion of tissue. The anodal after- 

 current is without exception stronger than the kathodal as I had 

 previously found. But further, the light magnet of the galvano- 

 meter brought into view a new fact, viz. : the appearance, before the 

 anodal after-current, of a short + effect. The anodal after- 

 current is thus diphasic, i. e. first + , then ; the kathodal after-current 

 is entirely + . Moreover the anodal after-current is of long dura- 

 tion, the magnet after reaching the maximum of its deflection 

 returns slowly and incompletely, often remaining stationary, 

 whereas the kathodal + deflection ceases immediately and com- 

 pletely. 



In the case of muscle, (the sartorius stretched out on cork being 

 generally used in these experiments) the law of the extrapolar after- 

 currents, which are always very well marked, is in general the 

 same as in that of nerve. A fact, as we shall see, of great import- 



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