MAMMALIA. 



693 



the extent of tlie surface to be supplied, and escape from the skull 

 through the cranial plate of the ethmoid bone, which, from the 

 number of apertures that it offers for their passage into the nose, 

 richly merits the name of " cribriform," more especially in the 

 carnivorous quadrupeds possessed of the most acute smell. 



(801.) The interior of the nasal cavity is divided by a median 

 septum into chambers, in each of which a very large surface is pro- 

 duced by the complicated convolutions of the thin nasal plates of the 

 ethmoid (Jig .230, F ig. 320. 



a), and of the in- 

 ferior turbinated 

 bone (6), over 

 which the air is 

 made to pass in 

 its progress to the 

 lungs before it 

 arrives at the pos- 

 terior nares (c). 

 The whole of this 

 complication of 

 bony lamellae is 

 covered with a de- 

 licate and highly 



lubricated mucous membrane, wherein the olfactory nerves termi- 

 nate ; and from the figure given, representing the left nasal cavity 

 of a Lion, some idea may be formed of the acuteness of the sense 

 in question conferred upon the predaceous Garni vora. 



(802.) With this perfection of the olfactory sense a corre- 

 sponding mobility of the outer nostrils is permitted to the Mam- 

 miferous races. In the Reptiles and Birds the external apertures 

 leading to the nose were merely immoveable perforations in the horny 

 or scaly covering of the upper mandible ; but now the nostrils 

 become surrounded with moveable cartilages, and appropriate mus- 

 cles, adapted to dilate or contract the passages leading to the nose, 

 or even to perform more important and unexpected duties, as, for 

 example, in the proboscis of the Elephant. 



(803.) The CETACEA, as regards the conformation of their 

 nostrils, and indeed of the whole of their nasal apparatus, form a 

 remarkable exception to the above description. Inhabiting the 

 water as these creatures do, they are compelled to breathe atmo- 

 spheric air. Are they then to smell through the intervention of 



