288 THE SO-CALLED SECONDARY ELECTROMOTIVE 



Herr A. von Gendre of St. Petersburg- undertook to read one of the 

 galvanometers. The two galvanometer-circuits were closed at the 

 2 3 same moment by means of a commutator, ar- 



ranged so that one was connected with i and 

 6, the other with 4 and 5. The commutator 

 j_ : had a paraffin bed instead of the ordinary 



wooden one, this excellent insulating material 

 5 6 being readily workable on the lathe. The two 



cups 2 and 3 were in the battery-circuit, and on the commutator 

 being turned to that side were connected by means of a copper arc. 

 The connections between the three copper arcs, indicated in the 

 figure by dotted lines, were of paraffin. Further, the battery, of 

 from 1-18 zinc carbon elements, stood upon paraffin feet. 



For the experiments on nerve, as a rule two sciatics were used, 

 joined together in such a way that the central end of one lay in 

 connection with the peripheral end of the other. This was in order 

 to eliminate as completely as possible the difference in the be- 

 haviour of nerve, stated by du Bois-Keymond to depend on the 

 centrifugal or centripetal direction of a current. For the experi- 

 ments on muscle, the groups of gracilis and semimembranosus were 

 used, the left and right groups being left in their natural attach- 

 ments to the symphysis ; and hooks fastened to ivory pegs by 

 silk thread were attached to the muscle groups and immovably 

 extended them. 



The leading-in contacts were at the two knee ends respectively, 

 and the two pairs of leading-off electrodes were brought as close as 

 possible to these, each pair being thus in connection with the lower 

 division of a muscle group, so that du Bois-Reymond's asserted 

 difference in the behaviour of the upper and lower part of the 

 muscle might be eliminated from the experiment. 



With nerve there occurred no marked difference in the deflections 

 of the two led-off regions attributable to the direction of the polar- 

 ising current ; that is to say, it made no difference as regards the 

 after-current whether the led-off region lay in the neighbourhood of 

 the anode or in that of the kathode. 



Example. Two sciatic nerves placed together in the manner before 

 described. The schema indicates the position of the electrodes (the 

 leading-off electrodes are marked thus \ ). 



c c' d d' 



5 I 8 | 40 I 8 | 5 



