OF PISHES. 47 



ORGANS OF SENSE. 



Hearing and seeing are probably the most per- 

 fectly developed of their senses. The machinery 

 of the internal ear is tolerably well understood, it 

 being satisfactorily ascertained that fishes are only 

 susceptible of simple sounds.* 



A DISSECTION OF THE EAR OF A HADDOCK, WHICH BEARS 

 A STRONG RESEMBLANCE TO THE LABYRINTH OF THE HU- 

 MAN EAR. 



c 



A. The sacculus vestibuli. 



B. The bony concretion which lies within, and which, by 

 its vibration, increases the impulse on the acoustic nerve. 



C. The auditory nerve, passing to be distributed on the 

 sacculus vestibuli, and the extremities of the semicircular 

 canals. 



D D D. The semicircular canals, three in number, ar- 

 ranged very much as they are in quadrupeds. 



E. One of the extremities of the semicircular canals, in 

 which a twig of the auditory nerve is seen to be expanded. 



F. This is a smaller portion of the same nerve. 



* Fishes have no external ear, nor is there any visible open- 

 ing, except in the skate. But there have been so many 



