XI 



ELECTRICAL FISHES 



373 



Fig. 241, a). According to Sachs, the transverse section of 

 the electrical plate exhibits the following layers from the front, 

 posteriorly (Fig. 242). Next to the anterior papillar layer 

 (stratum papillare anterius) comes a clear and perfectly structure- 

 less stratum, termed by Sachs the intermediate layer (stratum 

 intermedium), corresponding essentially with Pacini's parte fonda- 

 mentale. This is succeeded by the nervous layer (stratum 

 nerveum), which, apart from the processes of the posterior star- 



of a 



homogeneous 



gray 



colour. It 



cells which traverse it, is 

 gives off the posterior 

 papillae, and the thorn-like 

 papillae, forming collect- 

 ively the stratum papillare 

 posterius. The electrical 

 nerves end at the nervous 

 layer, as will be described 

 below. Transparently 

 homogeneous in the fresh 

 state, the papillae become 

 granulated within even 12 

 minutes after removal from 

 the living animal, while a 

 sharp boundary line (PL) 

 appears inside the inter- 

 mediate layer, dividing it 

 into two tolerably equal 

 halves. Cleavage of the 

 plate usually occurs at 

 these " Pacinian lines," 

 which appear in osmic preparations as a sharp dark streak in a 

 broad, light zone. Sachs found " a substance resembling spider- 

 web " between the anterior papillae, " consisting of meshes of fine 

 threads with small nuclear -like structures." Pacini detected 

 nerves upon the transverse septa only, where Sachs also noted 

 them plentifully, but in addition discovered their terminal branches 

 between the thorn papillae, and traversing the posterior cavity 

 of the compartment, to end finally, after loss of the medullated 

 sheath, in the plate itself. 



The posterior surface of the plate exhibits in transverse 

 section (with osmic preparations) the striation (or punctuation as 



FIG. 242. T.S. of electrical plate of Gymnotus; L.S. of 

 organ. (Sachs.) 



