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SCIENTIFIC NEWS. 



[Dec. 7, 1 838. 



McLean, of Lochbuey, and business was concluded by 

 the exhibition of a skeleton of the Great Auk (Alca im- 

 pciinis) by the Secretary. 



GLASGOW NATURAL HISTORY SOCIETY. 

 On November 13th Professor Cossar Ewart delivered a 

 lecture, under the auspices of this Society, on the Electric 

 Organs of Fishes. 



Professor Cossar Ewart said there were few if any 

 structures in the whole realm of nature which, in addi- 

 tion to perplexing and puzzling the naturalist, had at- 

 tracted more general attention than the electric organs of 

 fishes. Aristotle seemed to have pondered long the 

 peculiar force by which the electric ray numbed the 

 fishes that came within its reach, and Darwin, after long 

 and careful consideration, came to the conclusion that the 

 electric organs offered a special difficulty to his theory of 

 natural selection. And although, as the result of numerous 

 investigations, a considerable increase had recently been 

 made to our knowledge of these organs, it was still im- 

 possible to account for their origin, in some cases to offer 

 an opinion as to their function, or even to say whether 

 they were progressive structures or mere useless vestiges. 

 Proceeding, the lecturer showed how the torpedo and 

 other electric fishes fascinated the Greeks and to a less 

 extent the Romans, and how they held their ground 

 during the dark ages. One of the most noteworthy facts 

 about electric organs, he went on to say, was that they 

 were only found among fishes, and that although there 

 were hundreds of different kinds of fishes there were 

 practically only three kinds that were known to have 

 electric batteries sufficiently powerful to be of any evident 

 use. These were malapterurus of the Nile and other 

 African rivers, the gymnotus of South America, and the 

 torpedo found at times in our own waters and in con- 

 siderable numbers in the Mediterranean and the Atlantic. 

 Of the others in which electric organs were known to 

 exist were the once sacred oxyrhynchus of the Nile, and 

 the skates and rays which abound round the coast of Scot- 

 land. The malapterurus was a quaint-looking fish, with 

 a fatty dorsal fin like the salmon, and six long barbules 

 around the snout. It was said sometimes to reach a 

 length of four feet. In this fish the electric battery was 

 in the form of a continuous subcutaneous jacket or tunic, 

 which invested the whole body, with the exception of the 

 head and fins. It consisted of a countless number of 

 minute cells from which electricity was thrown off at will. 

 The gymnotus was a soft-skinned, sluggish creature, with 

 small, stupid-looking eyes flattened back, and long ventral 

 fin. It sometimes reached a length of six feet, and as 

 the electric batteries occupied nearly two-thirds of the 

 entire fish, one could easily understand how much it was 

 dreaded by the natives of the Orinoco region, and how 

 ordinary fishes gave the electric eel a wide berth. The 

 gymnotus had four batteries — two large and two small — 

 on each side of the body, supplied by about 200 pairs of 

 nerves. The batteries were so powerful that a shock 

 from a large, active fish was strong enough to strike 

 down a man and numb away his consciousness for 

 several hours. The torpedo was of special interest, 

 because we were beginning to understand all the steps 

 through which its organ had passed during its long and 

 gradual evolution. Some of the species attained a great 

 size. There was one, the giant torpedo, over four feet in 

 length, which when cast ashore at Cape Cod, was said 

 often by its unexpected shocks to strike down the unwary 



fishermen when they attacked it with their harpoons and 

 boathooks. The shock of the common British torpedo 

 was sufficiently strong to kill a duck, and when the organ 

 was connected with a telephone the discharges first pro- 

 duced a croaking sound, but as the fish got excited each 

 discharge was accompanied by a pronounced groan. The 

 electricity discharged from the torpedo's batteries be- 

 haved like ordinary electricity, rendering the needle mag- 

 netic and emitting sparks, and it might even be used in 

 charging a Leyden jar. But it should be specially noted 

 that the living battery of fishes differed from the ordinary 

 batteries. A Leyden jar or a voltaic pile had no influence 

 on the electricity it contained, while the electricity of the 

 torpedo was entirely under the control of its will, the 

 torpedo refusing to give a shock at one time, but readily 

 discharging its batteries at another. What was perhaps 

 still more remarkable, there were two large lobes in the 

 brain of the torpedo which regulated the production, 

 storage, and discharge of the electricity. These electric 

 lobes were composed of numerous giant nerve cells, from 

 which numerous nerve fibres extended to pass direct to 

 the batteries. When the electric lobes were destroyed 

 or the nerves passing from them were divided the torpedo 

 was rendered as helpless as an engine without steam. 

 The lecturer then proceeded to describe the structure of 

 the electric organ of the torpedo. He stated that the 

 battery consisted of an enormous number of columns or 

 prisms — in the ordinary torpedo from 400 to 500, in the 

 American about 1,000, making in the two batteries 2,000 

 columns for storing electricity. In each of the 500 

 columns there were about 600 electric plates, so that in 

 the ordinary torpedo there might be about 300,000 elec- 

 tric plates altogether, and in the giant torpedo some 

 500,000. These plates were supplied with an enormous 

 number of nerve fibres, so fine and dividing more and 

 more that with the highest power of the microscope it 

 was impossible to trace them. Each of these tissues was 

 connected with the electric lobes in the brain, and when 

 cut across were seen to be made up of a large number of 

 nerve cells. The lecturer described in detail the struc- 

 ture of the electric plate, and went on to say that the 

 electric organs claimed special attention, not only because 

 of 'their remarkable structure and still more remarkable 

 properties, but because their very existence was a mys- 

 tery. Mr. Darwin found the electric organs a special 

 difficulty to his theory of natural selection for two reasons 

 — he was able neither to understand their individual nor 

 their ancestral history. That the electric organs had 

 been gradually built up as the torpedo and electric eel 

 became more and more specialised, Darwin had no 

 doubt ; but he was unable to account for their origin by 

 his law of natural selection. And before proceeding he 

 emphasised the difference between evolution and natural 

 selection. We spoke of the fact of evolution, but the 

 theory of natural selection, for while all naturalists now 

 agreed that animals and plants had been evolved, there 

 was still some diversity of opinion as to the method by 

 which the evolution had been effected. In reference to any 

 plant or animal it would be said by most naturalists that 

 it was slowly evolved out of a mass originally shapeless 

 of growing protoplasm by means of natural selection 

 operating on fortuitous variations. As to the guiding 

 hand, science must be absolutely speechless. In asking 

 science to tell us what was the cause of causation, we 

 were asking her to cross an impassable channel, to pass 

 from the domain of fact to that of belief, a feat which if 

 essayed must inevitably end in failure. Returning from 



