112 CLASS-BOOK OF ZOOLOGY. 



branous tubes, united like the cells of a honey-comb, 

 which are filled with a slimy substance, and through 

 which pass numerous nerves. 



§ 468. These tubes are mostly six or five sided, some of 

 them square : 1 ,200 have been found on one side of a 

 Torpedo, or 2,400 on both sides : they may be compared 

 to charged electric jars, or to an electrical battery, for 

 they are charged with the electric fluid. 



§ 469. The nature of this curious phenomenon was for 

 a long time unknown. It was discovered by confining a 

 duck in a vessel with a Torpedo ; and as the bird, after a 

 few hours, was found dead, the electric power of the fish 

 was ascertained. 



§ 470. The Shark has a cartilaginous skeleton, gills 

 without cover, two fins on the back, a mouth generally 

 placed far beneath' the end of the nose, and the upper part 

 of the tail longer than the lower. 



§ 471. The mouth of the Shark is furnished with a six- 

 fold row of flat, triangular, finely serrated and exceedingly 

 sharp teeth, which lie quite flat in the mouth ; but which, 

 when seizing its prey, are raised with the aid of muscles, 

 by which they are joined to the jaw. 



§ 472. Sharks may be called the tigers of the sea, for 

 they are the most ferocious and dangerous of the finny 

 tribes. They kill and devour every living thing that 

 comes in their way. Their insatiable voracity may be 

 owing to the great quantity of gastric juice with which 

 they are supplied, causing them to digest very rapidly ; as 

 well as to the Tape, and other intestinal worms, which are 

 always found in great numbers in their intestines. 



§ 473. In order to discover their victims at a distance, 

 Sharks are provided with a powerful sense of smell ; 

 hence at sea they are frequently seen swimming behind 

 vessels, for the purpose of devouring what may drop or 

 be thrown overboard. 



§ 474. There is no genus of fish which equals the genus 

 Shark in dimensions and weight. We have accounts of 

 White Sharks which measured thirty feet, and weighed 

 more than a thousand pounds. They are found in all the 

 warmer seas. 



