SMELL. 



359 



Horse, for example, the turbinated bones are of a 

 large diameter, and extend the whole length of the 

 prolonged nostrils. Their structure is exceedingly 

 intricate ; for while they retain externally the ge- 

 neral shape of an oblong spiral shell, they are 

 pierced on all their internal sides with numerous 

 perforations, through which the membrane, toge- 

 ther with the fine branches of the nerves, passes 

 freely from one side to the other. The cavities 

 resulting from the convolutions are intersected by 

 unperforated 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 similar 

 to that just described; but the convolutions are 

 double, with an intermediate partition, so as to 

 resemble in its transverse section the capital of an 

 Ionic column. They are shown at t, Fig. 384, 



which exhibits the transverse section of the nostrils 

 of a sheep.* 



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

 exist, situated immediately behind the ordinary nostrils, and com- 

 municating- with them. These accessory nostrils are conjectured to 



