THE TORPEDO. 



39 



gradually to the tail. The teeth are small and obtuse, but each has a slight transverse ridge which is 

 not seen in the previous genus. There are twelve species found in the warmer seas. The skin is 

 usually coarsely granular, and covered with a series of tubercles, which often have large compressed 

 spines in the median line. The mouth is commonly straight, but is occasionally arched, and is fre- 

 quently longer than the nostril. Specimens of Rhinobatus yranulatus from India, in the British 

 Museum, have a length of seven feet, but jaws of a large example are fifteen inches wide. Most 

 of the species appear to be smaller than this. Trygonorhina is an Australian genus, distinguished 

 by the great width of the nasal valves. 



FAMILY III. TORPEDINID^E. 



The Torpedo family includes six genera, which are all distinguished by possessing electric 

 organs formed of hexagonal columns, which extend vertically, and are spread between the pectoral fins 

 and the head. They all have the nasal valves confluent, with a quadrangular flap or lobe, as in 

 Trygonorhina. The trunk is always a broad smooth disc. 



THE GENUS TORPEDO. 



The Torpedo has the body in front of the ventral fins more or less transversely ovate. The 

 surface of the body is smooth, soft, and somewhat rounded. There are two small dorsal fins placed 

 on the tail, which ends in a caudal fin having the lobes above and below nearly equal. Where the 

 Torpedo marmorata occurs on the British coast it is familiarly known as the Cramp-fish, Numb-fish, 

 and Electric Bay. When it is grasped by the hand a creeping sensation is felt in the whole limb up 

 to the shoulder, accompanied by violent trembling and sharp pain in the elbow. As its vitality declines, 

 the electric properties are lost, and are entirely wanting in the dead fish. The shock is sufficient to 

 kill a duck, and in one of the early experiments made by Mr. Walsh, who placed a Torpedo on a wet 

 napkin, the shock was felt by five persons, who received it from a wire extending from one end of the 

 napkin into a basin of water, and transmitted it by putting a finger of each hand in similar basins. There 

 are two electric organs placed on each side of the head and gills. They consist of many perpendicular 

 prisms, which are mostly hexagonal and form large flattened organs having the shape of kidneys. Each 

 column in the living fish appears like a mass of 

 clear trembling jelly. These cells occupy the 

 thickness of the body between the dorsal and ven- 

 tral covering. Hunter counted 470 columns in 

 each organ, and says that the partitions between 

 them are full of arteries which bring the blood 

 direct from the gills. These organs appear to con- 

 vert nervous energy into electricity. The nerves 

 which extend through them are an electric branch 

 of the trigeminal or fifth nerve, and four nerves 

 which are branches from the side of the medulla 

 oblongata, or hindermost part of the brain, each as 

 thick as the entire spinal cord itself. These nerve 

 trunks subdivide and penetrate into the partitions 

 between the columns. It has been taken on many 

 parts of the British coasts, but more frequently in 

 the English Channel than elsewhere. Specimens 

 taken in Cornwall have sometimes weighed a 

 hundred pounds, but usually they weigh only half 

 as much. An example which weighed forty-five 



pounds was forty-one inches and a half long by twenty-nine inches and a half broad, but on the following 

 day its dimensions had altered to forty-two inches by thirty, though it then weighed only forty-three 

 pounds and a half. After death the plump appearance of its upper surface is lost, and the lower border 

 curls upward. It is usually taken in the trawl, but sometimes with the line. The colour is a dark 

 brown, which is lighter round the eyes. The specimens which occur in the Mediterranean are usually 



TOKI'EDO MARMORATA. 



