272 



NA TURE 



[January 19, 189; 



Even the first and smallest of the electric nerves shows 

 a great number of nerve fibres collected into bundles 

 which on transverse section appear as if perforated by 

 numerous small openings — each apparent aperture being 

 a nerve fibre. I counted about 8039 fibres in the first 

 electric nerve, in the second or largest about 23,770 ; in 

 all four nerves about 58,318 fibres. This total exceeds 

 that of the ganglion cells by at least 4000, but the dis- 

 parity of number is probably to be accounted for by the 

 impossibility of getting an exact total from a series of 

 sections where the cells are very often dragged away by 

 the knife. 



The ganglion cells of the Gymnotus, or electric eel, are 

 disposed in a different manner. Behind a short portion 

 at the anterior end of the spinal cord where ordinary 

 cells are found, the grey substance contains large rounded 

 ganglion cells, the most anterior of them forming a semi- 

 circle around the central canal of the cord. Since these 

 first cells extend in front of the most anterior electric 

 nerves, a transverse section of this region shows no axis 

 cylinders leaving the grey substance, all being directed 



Fig. 3.— Communicating Electric Cells in the Spinal Cord of Mormyrus 



downwards to the gathering place of the first electric 

 nerve roots, and therefore must be cut off. If, however, a 

 transverse section be made in the middle portion of the 

 cord the whole grey matter is seen to be packed with 

 electric cells and their axis cylinders are seen passing 

 very straight and undivided to join the electric nerve roots 

 at once. The other processes of the cells are so pale and 

 fine that it is impossible to recognize them sufficiently 

 well in a complete section. Since the electric batteries 

 extend along both sides of the tail to its very end, the 

 electric nerves and their ganglionic centres have a similar 

 extension. The electric cells form a continuous column in 

 the spinal cord, but it is very slender, therefore, notwith- 

 standing the great longitudinal extent of the electric 

 centre, the number of cells is not so very great. I esti- 

 mated the total number of cells to be about 60,000 — not 

 many more than the estimated number in the Torpedo. 



The genus Mormyrus, whose electric power was 

 doubted until quite recently, resembles the Gymnotus in 

 the structural arrangement of its electric apparatus. I 

 was fortunate enough to find the ganglion cells for the 



NO. I 2 12, VOL. 47] 



electric nerves in the spinal cord, where the tail is en- 

 dowed with the electric batteries, as seen in Fig. i. The 

 cells are very soft, and must be very carefully preserved 

 to show all their details. Their regular undivided axis 

 cylinders leave the cord-like motor roots, and form a 

 sort of plexus before leaving the vertebral canal. It is to 

 be considered as a very important fact, that broad pro- 

 cesses of the cells regularly intercommunicate on so large 

 a scale that their union into a complete system for 

 simultaneous action cannot be doubted. 



Fig. 3 shows such cells in the grey substance of the 

 spinal cord ; the intercommunicating processes can be 

 seen much more distinctly in the microscopic slide and 

 even in a photogram, than they appear in that figure. 



The axis cylinder of each cell being a well-defined 

 undivided process, the intercommunicating processes 

 must be regarded as protoplasmic in the sense expressed 

 by Deiters. Their general intercommunication cannot 

 have any other significance than to insure equality of 

 action in giving the impulse to the electric batteries. If 

 that statement be admitted the protoplasmic processes of 

 the cells must have a conducting function. 

 If that be true in the Mormyrus there is no 

 reason whatever why it should be otherwise 

 in other vertebrates. Yet Golgi maintains 

 that^he protoplasmic processes of nerve cells 

 are to be regarded as having a simply nutritive 

 and therefore a non-nervous function. 



There is another most remarkable fact in 

 the organization of the Mormyrus having 

 reference to the combined action of the 

 electric organs on both sides. The upper 

 as well as the lower electric nerves form a 

 decussation outside the vertebral canal re- 

 sembling the chiasma of the optic nerves. I 

 am not acquainted with any other instance 

 of motor nerves crossing the median plane 

 to the other side of the body outside the 

 cerebrospinal axis. In all other cases they 

 are outside the brain and the spinal cord 

 confined to their own side of the body to 

 insure the isolated action of each muscle 

 or group of muscles on that side. It is 

 therefore stated that in changing the motor 

 into an electric function these nerves at the 

 same time became liberated from the strict 

 rules of their predecessors. Certainly the 

 case of Mormyrus gives a very good idea 

 of the extraordinary power of adaptation to 

 function with which Nature is endowed ; but 

 who can say how this particular anatomical 

 arrangement could come about by gradual 

 variation t I consider this difficulty far 

 greater than that relating to the first development of 

 electric organs in general which is so frequently the 

 subject of reference. 



Since the celebrated investigations of Prof. E. du Bois- 

 Reymond have shown that the function of the muscular 

 system is intimately associated with electric currents it 

 is permissible to take them into account where muscle 

 and their derivatives are under consideration. 



I have shown elsewhere that most of the electric fishes 

 are liable to a degeneration of the muscular system, 

 seemingly caused— in part, at all events — by a certain 

 lazy mode of life (disuse of organs). We therefore find 

 along with fully developed electric tissue in the Gymnotus, 

 nests of muscles which have not arrived at perfection. 

 In the Mormyrus degenerating muscles in the forepart 

 of the electric organ suggest the impression that the 

 process of transformation is still going on. Still more 

 is this the case in the common Raja. 



Moreover, we know that the peculiar degeneration of 

 muscular tissue into electric tissue destroys the contract- 

 ile power of the muscles, but does not interfere with their 



