SUBMENTAL FILAMENTS: GYMNOTID EEL 687 
After the removal of the dermis, the filaments appear as small 
white cylinders which are swung at the base of each operculum, 
and are attached only at their ends. 
The filament consists of an outer cylindrical sheath of connec- 
tive tissue, arranged in layers. Inside this cylinder is a series 
of about forty parallel discs placed vertically to the outer sheath 
of connective tissue which supports the discs, and from this layer 
small strands of connective tissue support the nerve fibers and 
blood vessels. 
Fig. 1 Sagittal section of submental filament. Photograph. A, connective 
tissue; B, electroplax; D, papillae on electric surface; H, electrolemma. 
The main nerve, supplying each filament, enters the organ at a 
point near the basal angle of the operculum, and traverses the 
filament in a sinuous path along the ventral side between the con- 
nective tissue and the plates. This nerve divides, sending branch 
nerves to each disc. ‘These branch nerves ascend the posterior 
surfaces of the discs and cross to the anterior surface of the adja- 
cent discs. Entering the organ with, and paralleling the main 
nerve, is the main blood vessel which also sends branches to each 
plate. 
