ELECTRICITY. 



475 



Descriptive rectly across from its outer edge to the semicircular 

 Electricity, cartilages. They are covered, above and below, by 

 " v ~~ "" the common skin of the animal, under which there 

 On the elcc- j s a t hj n f^da spread over the whole organ. This is 

 " s composed of fibres, which run longitudinally, and in 

 " *"" the direction of the body of the animal. These fibres 

 appear to be perforated in innumerable places, which 

 gives the fascia the appearance of being fasciculated. 

 Its edges all around are closely connected to the skin, 

 and at last appear to be lost, or to degenerate into the 

 common cellular membrane of the skin. Immediate- 

 ly under this is another membrane exactly of the same 

 kind; the fibres of which, in some measure, decus- 

 sate those of the former, passing from the middle line 

 of the body outwards and backwards. The inner edge 

 of tlu's is lost with the first described ; the anterior, 

 outer, and posterior edges, are partly attached to the 

 semicircular cartilages, and partly lost in the common 

 cellular membrane. . 



" This inner fascia appears to be continued into the 

 electric organ by so many processes, and thereby makes 

 the membranous sides, or sheaths of the columns, 

 which are presently to be described ; and between 

 these processes the fascia covers the end of each co- 

 lumn, making the outermost, or first partition. Each 

 organ of the fish under consideration is about five inches 

 in length, and at the anterior end three in breadth, 

 though it is but little more than half an inch broad 

 at the posterior extremity. Each consists wholly of 

 perpendicular columns, reaching from the upper to the 

 under surface of the body, and varying in their length, 

 according to the thickness of the parts of the body 

 where they are placed ; the longest column being about 

 an inch and a half, the shortest about one-fourth of 

 an inch in length, and their diameter about two-tenths 

 of an inch. 



" The figures of the columns are very irregular, va- 

 rying according to situation, and other circumstances. 

 The greatest number of them are either irregular hex- 

 agons, or irregular pentagons ; but, from the irregu- 

 larity of some of them, it happens, that a pretty regu- 

 lar quadrangular column is sometimes formed. Those 

 of the exterior one are either quadrangular or hexa- 

 gonal ; having one side external, two lateral, and ei- 

 ther one or two internal. In the second row they are 

 mostly pentagonal. Their coats are very thin, and seem 

 transparent, closely connected with each other, having 

 a kind of loose network of tendinous fibres passing 

 transversely and obliquely between the columns, and 

 uniting them more firmly together. These are most- 

 ly observable where the large trunks of the nerves pass. 

 The columns are also attached by strong inelastic fi- 

 bres passing directly from the one to the other. 



" The number of columns in different torpedos, of 

 the size of that now offered to the Society, appeared to 

 be about 470 in each organ ; but the number varies ac- 

 cording to the size of the fish. * These columns in- 

 crease, not only in size, but in number, during the 

 growth of the animal ; new ones forming perhaps every 

 year on the exterior edges, as they are much the small- 

 est. This process may be similar to the formation of 

 new teeth in the human jaw, as it increases. Each co- 

 lumn is divided by horizontal partitions placed over 

 each other at very small distances, and forming nume- 

 rous interstices, which appear to contain a fluid. These 

 partitions consist of a very thin membrane, considera- 



bly transparent. Their edges appear to be attached to Descriptive 



one another, and the whole is attached by a fine cellu- ^lectrioty^ 



lar membrane to the inside of the columns. They are 



not totally detached from one another. I have found On tle el(-c " 



them adhering at different places, by blood-vessels pass- 



ing from one another. i 



" The number of partitions contained in a column of 

 one inch in length, of a torpedo which had been pre- 

 served in proof spirit, appeared, on a careful examina- 

 tion, to be 150; and the number in a given length of 

 column, appears to be common to all sizes in the 

 same state of humidity ; for by drying them they may 

 be greatly altered. Whence it appears probable, that 

 the increase in the length of a column, during the 

 growth of the animal, does not enlarge the distance be- 

 tween each partition in proportion to that growth ; but 

 that new partitions are formed and added to the extre- 

 mity of the column from the fascia. 



" The partitions are very vascular ; the arteries are 

 branches irom the veins of the gills, which convey the 

 blood that has received the influence of respiration. 

 They pass along with the nerves to the electric organ, 

 and enter with them ; they then ramify, in every di- 

 rection, into innumerable small branches on the sides 

 of the columns, sending in from the circumference all 

 around, on each partition, small arteries, which ramify 

 and anastomose on it ; and passing also from one parti- 

 tion to another, anastomose with the vessels of the ad- 

 jacent partitions. The veins of the electric organ pass 

 out close to the nerves, and run between the gills to 

 the auricle of the heart. ^^ 



" The nerves inserted into eachelctric organ, arise 

 by three very large trunks from the lateral and poste- 

 rior part of the brain. The first of these, in its pas- 

 sage outwards, turns round a cartilage of the cranium, 

 and sends a few branches to the first gill, and to the 

 anterior part of the head, and then passes into the or- 

 gan towards its anterior extremity. The second trunk 

 enters the gills between the first and second openings, 

 and, after furnishing it with small branches, passes in- 

 to the organ near the middle. The third trunk, after 

 leaving die skull, divides two branches which pass to 

 the electric organ through the gills ; one between the 

 second and third openings, the other between the third 

 and fourth, giving small branches to the gill itself. 

 These nerves having entered the organs, ramify in eve- 

 ry direction between the columns, and send in small 

 branches on each partition, where they are lost. 



" The magnitude and the number of the nerves be- The nerve* 

 stowed on these organs, in proportion to their size, very nume- 

 must, on reflection, appear as extraordinary as the phe- rous in ^ ' 

 nomena they afford. Nerves are given to parts either c ' ectric *' 

 for sensation or action. Now, if we except the more organ< 

 important senses of seeing, hearing, smelling, and taste, 

 ing, which do not belong to the electric organs, there 

 is no part, even of the most perfect animal, which, in 

 proportion to its size, is so liberally supplied with 

 nerves ; nor do the nerves seem necessary for any sen- 

 sation which can be supposed to belong to the electric , 

 organs. And, with respect to action, there is no part 

 of any animal, with which I am acquainted, however 

 strong and constant its natural actions may be, which 

 has so great a proportion of nerves. If it be then pro- 

 bable, that these nerves are not necessary for the pur- 

 poses of sensation or action, may we not conclude, that 

 they are subservient to the formation, collection, or 



In * very luge torpedo, weighing 731bs. and 14 feet in length, the number of columns in one electric organ wer 1182. 

 do WM found on tht British coast, and has been fully described by Mr Walsh, in the Phil. Tram. 17 T4, p. 4G4. 



Thin torpt- 



