ELECTRICITY. 



47 



Descriptive For further information respecting the gymnotis elec- 

 ecmcitjr. tricus, see Richer, Mem. Acad. Par. 1677, torn. i. p. 116. 

 ""'""""' Id. torn. vii. par. 2. p. 92. Condamine, Relation d'un 

 Voyage, %C. Mem. Acad. Par. 1745. p. 466. Perrere, 

 Htstoire de France Equinoxiale. Ferrnin, Description 

 de Surinam, torn. ii. p. 261. Muschenbroek, Mem. 

 Acad. 1760, Hist. p. 21. Bancroft's History of Guiana. 

 Schilling, Mem. Acad. Berlin, 1775, p. 6. Schilling, 

 Diatribe de Morbo, in Europa pene igtioto Jaws dicto, 

 1770. Williamson, Phil. Trans. 1775, vol. Ixv. p. 94. 

 Garden, Phil. Trans. 1775, vol. Ixv. p. 102. Walsh, 

 Phil. Trans. 1775. Hunter, Phil. Trans. 1775, vol. Ixv. 

 p. 395. Van Swinden, Recveil des Memoires sur I'A- 

 nalogie de I'Electricite et du Magnetisme, 1786, vol. i. p. 

 439. Lacepede, Hist. Naturelle des Poissons, torn. ii. 

 Bertholon, DC C Electricile du Corps Humain, Paris, 

 1786, torn. i. p. 171. 



3. On the Electricity of the Silurus E/ectricut. 

 ^df'of'the The silurus electricus is a fish about 20 inches long, 

 lunu dec! ver y broad in the fore part, and of a cinereous colour, 

 tricus. with a few blackish spots towards the tail. It was 

 found in some of the rivers of Africa, particularly in 

 the Niger by Adanson, and in the Nile by Forskal; 

 and when it is touched it gives an electrical shock, 

 which is much feebler than that of the torpedo or the 

 gymnotus. When laid on one hand, and touched with 

 an iron rod six feet long held in the other, the shock is 

 distinctly felt. The inhabitants on theNile call itRaasch, 

 the same name which they give to the torpedo ; and the 

 Egyptians eat its flesh, and salt its skin, to which they 

 ascribe an aphrodisiac quality. This fish is described by 

 Forskal under a wrong name, and was found to be a si- 

 lurus by Broussonet. This fish is called Onanienar by 

 PLATE the Negroes, from its electrical property ; snALeTrem- 

 CCXLVI. bifur du Senegal by the French. The fish is represent. 

 F - 3- ed in Plate CCXLVI. Fig. 3. 



The anatn- According to M. Geoffrey, who examined the elec- 

 nicil stnic- trical organs of this fish, they are much less complica- 

 ted than those of the torpedo and gymnotus. In the 

 rgan. silurus, this organ lies immediately below the skin, 

 and stretches all round the body of the animal. The 

 organ is composed of a collection of cellular tissue, go 

 extremely thick and compact, that it resembles at first 

 a stratum of lard, till the microscope informs us that 

 it is composed of tendinous or aponeurotic fibres, inter- 

 woven with each other, and forming a reticulated 

 mass, of which the meshes may be distinctly seen. As 

 in the torpedo and gymnotus, these cells are filled with 

 an albuminous gelatinous matter. All communication 

 is prevented in the inside by ;i very strong uponeurosis, 

 extending over the whole reticulation, and adhering 

 very closely to it. It is also covered above this with a 

 thick layer of fat. The nerves distributed over the 

 electric organ of this fish proceed from the brain, and 

 are the same with those found in all other fishes under 

 the lateral line of the body. The two nerves of the 

 eighth pair have a direction and nature peculiar to this 

 species. Approaching each other as they issue from the 

 cranium, they descend and traverse the body of the 

 first vertebra. They first introduce themselves through 

 an orifice peculiar to each other, and then issue by 

 one aperture on the opposite side. After reascend- 

 ing, they suddenly separate, and proceed under each 

 of the lateral lines. They are then found lodged be- 

 tween the abdominal muscles, and the aponeurosis 

 which extends over the articulated organ. They then 

 end large branches beneath the skin, which proceed 

 to the right and left to the principal nerve. These 

 branches, which amount to twelve or fifteen on each 



side, penetrate the aponeurosis which lines the inniv 

 surface of the reticular tissue, and they are lost in the electricity^ 

 latter. See Adanson, Voyage au Senegal, 1757, p. 135; "V 

 Broussonet, Mem. Acad. Par. 1782, p. 692; Rozier 

 Observations, Sfc. vol. xxvii. p. 139 ; Geoffroy, Bulletin 

 de la Societt Philomalique, torn. iii. p. 169; Annales du 

 Museum d'Hist. Nat. ; and Phil. Mag. vol. xv. p. 126. 



4. On the Electricity of the Trichiurus Indicus. 



This fish inhabits the Indian seas, and possesses the o f* . tlle ''"" 

 electrical faculty like the silurus electricus. So far as *"",'; y u ^ us ' 

 we know, its electrical organs have not been examined indicus. 

 by anatomists. 



5. On the Electricity of the Telraodon Electricus. 



This fish was discovered, by Lieutenant William Pa- On the elec- 

 terson, to possess the power of giving an electric shock, tricityofthe 

 He met with it on his way to the East Indies, in the tet-raodon 

 Island of Johanna, one of the Comoro Isles. It is 7 electncus. 

 inches long, 2^ inches broad, and has a long projecting 

 mouth. It is of a dark brown colour on the back, of a 

 sea green colour on the belly, yellow on the sides, and of 

 a sandy green on the fins and tail. The body is cover- 

 ed over with red, green, and white spots, the latter being 

 particularly bright. The eyes of the fish are large, and 

 the iris is red, having its outer edge tinged with yellow. 

 Mr Paterson caught this fish in the cavities of the coral 

 rocks, where the temperature of the water was 56 or 

 60 of Fahrenheit. Having caught two of them in 

 a linen bag, he attempted to take one of them in his 

 hand, when he received so severe an electrical shock, 

 that he was obliged to quit his hold. He then carried 

 them to the camp, which was about two miles distant, 

 but on his arrival one of them was unfortunately dead, 

 and the other in such a state of debility, that he was very 

 desirous to establish without delay the existence of the 

 electrical faculty, by the evidence of others. He therefore 

 put it into a tub of water.and when the surgeon of the re- 

 giment endeavoured to lay hold of it between his hands, 

 he received a distinct electrical shock. The adjutant 

 afterwards touched it on the back with his finger, and 

 experienced a slight shock. See the Philosophical 

 Transactions for 1786, vol. Ixxvi. p. 382. 



SECT. VIII. On the Spontaneous Electricity of the 

 Human Body. 



WE have already had occasion, in our history of the on the 

 science, to mention several electrical phenomena pro-, spontaneous 

 duced on the human body. These, however, werq electricity of 

 obviously generated by friction, and have therefore no tllc '""" 

 connection with the present subject. Various install- y ' 

 ces have occurred in which sparks of electric light 

 have been evolved during the combing of the hair, 

 the rubbing of the breast and arms, and the pulling 

 off of the under garments; but in these cases the elir- 

 tricity is excited by friction, and is strong or weak in 

 different cases, according to the constitution of the indi- 

 vidual, the dryness of the skin, the nature of the clothes, 

 and the state of the surrounding air. 



M. de Saussure made a great number of experiments E,.;. 

 on the electricity of his own body, which he examined nienuof M. 

 by means of Volta's electrometer find condenser, but he de Saustuw . 

 does not seem to have observed that kind of electricity 

 which is properly entitled to the name of spontaneous. 

 Ashe never could discover any electricity in his own body 

 when he was perfectly naked, he concluded that it was 

 produced by the friction of the clothes against the skin. 

 He could never find any electrical indications when hi, 

 clothes were cold, or when his body wax in a state of 



