392 



THE SENSORIAL FUNCTIONS. 



impression made on those nerves. The mechanical 

 effect of an apparatus of this kind is shown by the 

 simple experiment, mentioned by Camper, of en- 

 closing a marble in a bladder full of water, and 

 held in the hand ; when the slightest shaking of 

 the bladder will be found instantly to communicate 

 motion to the marble, the reaction of which on 

 the bladder gives an unexpected concussion to the 

 hand. 



The ear of Fishes contains, in addition to the 

 vestibule, the three semicircular canals, which are 

 in general greatly developed.* An enlarged view 

 of the membranous labyrinth of the Lophius pisca- 

 torius is given in Fig. 403, showing the form and 



complication of its parts, which are represented of 

 twice the natural size, x, y, z, are the semicircular 

 canals, with their respective ampullae (a, a, a), m 

 is the Sinus medianus, or principal vestibular sac, 

 with its anterior expansion, termed the Utricle (u). 

 The Sacciilus (s) has, in like manner, a posterior 



* In the Lamprey, these canals exist only in a rudimental state, 

 appearing as folds of the membrane of the vestibule ; and there are 

 also no cretaceous bodies in the vestibular sac. 



