M. Robin on a jjeculiar Organ found in the Raj/s. 51 



extend into the partitions of each series of discs infinitely subdi- 

 viding. From these subdivisions part the filaments which pene- 

 trate between the partition which separates each disc from that 

 with which it is in contact. This filament expands opposite to 

 the anterior face of each disc, but never does a single one pene- 

 trate into the substance of the disc. The nerves spread out on 

 the mternal surface of the partition between it and the disc. No 

 single thread ever ramifies against the posterior face of the disc ; 

 we shall soon see that this surface receives only vessels. 



The elementary fibres of the nervous filaments have a double 

 character ; that is, they are true elementary nervous tubes tra- 

 versed by a semifluid substance which escapes in di'ops of variable 

 forms from their extremities when torn across. [These observa- 

 tions however Avould require to be verified upon animals fresh 

 captm'ed. ] 



The elementary tubes which spread out against the prism are 

 from 0'°-01 to 0-013, that is to say, half the diameter of the ele- 

 mentary tubes measm-ed on the nerves at the point of their pe- 

 netration into the apparatus. The elementary nervous tubes do 

 not terminate in a net-work, but actually in very large mesheSj 

 to effect which they fork out several times into two or three 

 branches and anastomose by inosculation. 



These facts rest on the clearest evidence, being easily proved 

 even with a magnifying power of 100 diameters. The semifluid 

 nei-vous substance contained in these elementary tubes may be 

 made to flow out, and be seea to penetrate into each of their sub- 

 divisions and anastomoses. These anastomotic terminations of 

 the elementary nervous tubes have already been proved to exist 

 by Savi, in his " Anatomical Investigation of the Torpedo (1844) .•" 

 He has also proved this fact in the partitions which separate the 

 discs of gelatinous substance of the electric apparatus of this 

 fish. 



The last facts which I have just established exhibit a still 

 greater analogy between the organ in question and the apparatus 

 of the electric fishes. It is true that these nerves proceed from 

 the termination of the spinal marrow, that is to say, from the 

 Cauda equina, but the same fact takes place in the Gymnofus, the 

 most potent in its discharges of the electrical fishes, whose elec- 

 trical organs however, according to Hunter, do not receive a mass 

 of nerves proportionably so considcraljle as those of the Torpedo. 

 In the Kay, as in the Gymnotus, the mass of the nerves sent to 

 the tlectric aj)paratu3 by each nervous pair, is at least as consi- 

 derable as those which they transmit to the skin and the muscles. 

 The lateral nerve does not in the Ray, any more than in the 

 Gymnotun, send any filament to the organ in question. 

 The nerves of the electrical apparatus of the Silums, examined 

 1:2 



