ANIMAL MECHANISM. 299 



Besides the sacs themselves, the porch is lined with a 

 membrane of exquisite texture, in which is conducted 

 the blood vessels that administer the blood to the contained 

 saculi, and also secrete their contained fluid, aqua 

 labyrintha or water of the labyrinth, further to be com- 

 mented upon. 



SEMICIRCULAR CANALS. 



These are properly a prolongation of the vestibule 

 the design evidently being to furnish surface for expand- 

 ing the auditory nerve, without carrying it onward 

 towards organs that would be affected by their presence. 

 No way could be devised, possibly, more strictly eco- 

 nomical, than to have a circular or semicircular canal, 

 curving in a little space, as in a very small solid bit of 

 bone. Precisely on this plan, are these canals they 

 are three in number. Let it be remembered in this 

 place, that the tympanum, including the vestibule, little 

 bones and semicircular canals, exclusively make up the 

 ear of fishes, and reptiles neither of these tribes have 

 an external ear, nor the cochlea, which still remains to 

 be elucidated. 



So much is necessary to the true perception of simple 

 sounds : the cartilaginous fishes, (sharks, eels, &c,) have 

 them, and are therefore capable of judging of the di- 

 rection and condition of different sounds. The Chinese 

 drive fish from the crevices of rocks to the angling 

 ground, by beating a gong. Pike and carp, reared in 

 artificially stocked ponds, both in Poland and France, 

 have been taught to come to a particular spot or border, 

 to feed, at the ringing of a bell. Serpents, abundant 

 evidence substantiates, are exceedingly excited by the 

 lively strains of music coiling themselves into a variety 

 of folds, and giving a tremulous vibration to the tail, 

 which long experience proves to be the result of a plea- 

 surable sensation, and not one of displeasure, rage or 

 pain. Egypt, of all countries on the globe, is the paradise 

 of serpent charmers, who never fail to astonish Europeans 

 by their tact in discovering the true characters and in- 

 stinctive propensities of the individuals constituting 

 their serpentine exhibitions. 



