SMELL. 



285 



which the membrane, together with the fine branches of the 

 nerves, passes freely from one side to the other. The ca- 

 vities resulting from the convolutions are inlersccted by un- 

 perforated partitions of extraordinary tenuity, serving both 

 to support the arches of bone, and to furnish a still greater 

 surface for the extension of the olfactory membrane. In 

 the Sheep, the Goat, and the Deer, the structure is very si- 

 milar to that just described; but the convolutions are double, 

 with an intermediate partition, so as to resemble in its trans- 

 verse section the capital of an Ionic column.* They are 

 shown at (t) in the transverse section of the nostrils of a 

 sheep in Fig. 384. 



In carnivorous quadrupeds the structure of these bones is 

 still more intricate, and is calculated to afford a far more ex- 

 tensive surface for the distribution of the olfactory nerve. 

 In the Seal this conformation is most fully developed, and 

 the bony plates are here not turbinated, but ramified, as 



* In a species of Antelope described by Mr. Hodgson, cavities exist, si- 

 tuated immediately behind the ordinary nostrils, and communicating- with 

 them. The accessory nostrils are conjectured to be useful to this excceding-- 

 ly fleet animal by facilitating its breathing, while it is exerting its utmost 

 speed; for the expansion of the nostrils opens also these posterior cavities, 

 the sides of which, being elastic, remain dilated. Journal of the Asiatic So- 

 ciety, Feb. 1832, p. 59. 



