442 THE SENSORIAL FUNCTIONS. 



ness of hearing. This is more particularly the 

 case with feeble and timid quadrupeds, as the 

 hare and rabbit, which are ever on the watch to 

 catch the most distant sounds of danger, and 

 whose ears are turned backwards, or in the 

 direction of their pursuers ; while, on the con- 

 trary, the ears of predaceous animals are directed 

 forwards, that is, towards the objects of their 

 pursuit. This difterence in direction is not 

 confined to the external ear, but is observable 

 also in the bony passage leading to the tym- 

 panum. 



The Cetacea, being strictly inhabitants of the 

 water, have no external ear; and the passage 

 leading to the tympanum is a narrow and wind- 

 ing tube, formed of cartilage instead of bone, 

 and having a very small external aperture. In 

 the Dolphin tribe the orifice wdll barely admit 

 the entrance of a pin ; it is also exceedingly 

 small in the Dugojig ; these structures being 

 evidently intended for preventing the entrance 

 of any quantity of water.* It is apparently 

 with the same design that in the Seal the pas- 

 sage makes a circular turn ; and that, in the 

 Ornithorhyncus paradoxus, it winds round the 

 temporal bone, and has its external orifice at a 

 great distance from the vestibule. The internal 



* It is probable that in these animals the principal channel 

 by which sounds reach the internal organ is the Eustachian 

 tube. 



