FISHES. 345 



branovis labyrinth, the cranium cannot transmit its oscillations to the 

 labyrinth, but in a feeble degree. The absence of a true cochlea and 

 its fibrous lamina, Avill not allow us to believe that the ear of fishes 

 can be affected by the difference of tones. It simply offers to the 

 physiologist, a very sensitive membranous apparatus, in which the 

 nervous filaments distributed in the ampullae of the semi-circnlar 

 canals, must participate in all the movements of the fluid in which it 

 is plunged, and in Avhich, those that are attached to the sacs and ves- 

 tibule must be still more vividly agitated, by the shocks communicated 

 by these movements to the stones contained in these cavities. 



It is therefore probable that fishes hear; that noise produces in 

 them a strong sensation, but that they cannot distinguish either the 

 infinite variety of tones, or those articulate sounds, with which quad- 

 rupeds, and birds appear to be so vividly struck. All that we learn 

 from experience, as to the degree in which fishes enjoy the faculty of 

 hearing, is shewn in their being easily frightened by sudden and 

 unvisual noises ; in the necessity which fishermen feel of observing 

 profound silence, in order not to put them to flight; and in their 

 habituating themselves to be called to receive food, and know the 

 sounds employed for that purpose. 



We have seen elsewhere, that the Romans had trained them to 

 know their own names ; but we are not aware, that the moderns have 

 carried their education to the same extent. 



As to the special apparatuses, which are only found in certain ge- 

 nera, such as the silures, cyprins, cobitcs, and lepidolepruses, which 

 have been looked upon as substitutes or analogies, for the tympanum, 

 and' small bones of the ear in mammalia, since these are only excep- 

 tionable organs, whicli are far from belonging to the entire class, we 

 shall refer their description to the chapter on the genera which are 

 provided with such organs. 



Nostrils. 



The nostrils of fishes are not so disposed, as to be passed over by 

 the air or water during respiration. They consist of two fossse hol- 

 lowed out towards the front of the snout, and lined with a pituitary 

 membrane, which forms very regular folds. In ordinary fishes, the 

 bone, which we regard as the nasal, covers them like a vault, and the 

 vomer, the maxillary, and intermaxillary contribute to support their 

 walls ; the first suborbitary forms their inferior border. 'Iheir form 

 is sometimes oblong, and sometimes oval or round. They are placed 

 either at the end of the snout or on the sides, sometimes on its superior 

 surface, and in the ray, and squalus, even on its inferior surface, near 

 the corners of the mouth. In the lamprey they are situated close 

 together on the top of the head, and open by a small common aper- 

 ture. In the majority of fishes, perhaps in all the osseous, they open 

 each by two orifices, one before and one behind, and sometimes at 

 some distance from each other ; this is called the double nostrils, a 

 denomination which is evidently improper, as they communicate only 

 with one cavity. 



The edges of the anterior orifice are often tubular as in the eel ; 



