Methylene blue filling of the dorsal giant fibres of the earthworm by electrophoresis

Multisegmental methylene blue filling of the three dorsal giant fibres in the nervous system of the earthworm was obtained by the use of electrophoresis. There was no difference in aldehyde fixed and unfixed tissue; due to its larger diameter, the median giant fibre could be stained over longer distances than the lateral ones. Accumulations of the dye were detected in the median giant fibre in the dorsal openings of the myelin sheath and at the origins of the ventral branches descending from both fibre systems. Since no significant axonal filling was observed by using several other dyes similar to methylene blue in diffusion and dialysis properties, the staining mechanism obviously depends on the specific binding sites of methylene blue in combination with the current. Therefore, the revealed phenomena provides evidence of a direct correlation between methyelne blue coupling and electrical coupling in the dorsal giant fibres of the earthworm.