in ELECTRICAL EXCITATION OF MUSCLE 211 



In the majority of the older experiments, where the current was 

 led in through metal wires, in direct contact with the muscle, there 

 can, of course, be no doubt as to the meaning of the terms anode 

 and kathode. So, too, in v. Bezold's experiments, the expression 

 " the closing excitation proceeds from the kathode, the opening 

 excitation from the anode," cannot well be misunderstood. But th 

 case is otherwise when, although metal conductors are used, the 

 current is led into the muscle via bones and tendons. Then the 

 expression quoted takes on quite another meaning. It is obvious 

 that the excitation cannot proceed in this case from those points 

 at which the metallic electrodes are in contact with animal tissues, 

 e.g. the bones or tendons ; but that the tendinous ends of the 

 muscle-fibres themselves are the real electrodes, and when, under 

 these circumstances, electrodes a're spoken of, it can only mean 

 that the current sets up a peculiar action at the points at ivhick 

 it enters or leaves the muscle-fibres. How easily misunderstandings 

 may arise through these ambiguities, is evident from the 

 consideration of certain experiments of Aeby (20) and Briicke 

 (23), which are intended to disprove v. Bezold's theory. The 

 former sent current through both legs of a frog still united by 

 the pelvis, so arranged that the wires which served as electrodes 

 were connected with the lower ends of the two legs. A piece of 

 the thigh-bone was cut out on either side subcutaneously, so that 

 the muscles of both thighs shortened at closure of the current, 

 but more so with a descending than with an ascending current. 

 Aeby deduced from this that the former lay nearer to the 

 negative as he thought, more active pole ; thereby, as Engel- 

 mann pointed out, confusing the real, or natural, electrodes of the 

 muscle with the artificial i.e. unreal electrodes of the entire 

 preparation. For obviously, in a thigh traversed by an ascending 

 current, the anode would occur at the knee, the kathode at the 

 pelvis, and vice versa in opposite cases. Briicke used a similar 

 preparation, only he removed the entire skin, with the extensor 

 muscles, together with the diaphyses of the thigh-bones. If he 

 gripped the two gastrocnemii with forceps, connected in circuit 

 with 6-10 small Daniell cells, the muscles of the thigh and leg 

 contracted on both sides. "In this case," says Briicke, "no 

 contraction waves could spread from the kathode to the flexors 

 of the thigh. It must be admitted that they contracted independ- 

 ently of all kathodic action, solely because they were traversed by 



