284 THE SENSOHIAL FUNCTIONS. 



brane.* A transverse and vertical section of these parts is 

 given in Fig. 3S3.t The turbinated bones are curiously 

 folded, and often convoluted in a spiral form, with the evi- 

 dent design of obtaining as great an extent of surface as pos- 

 sible within the confined space of the nasal cavity. This tur- 



binated, or spiral shape, chiefly characterizes these bones 

 among herbivorous quadrupeds: in the 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 

 general shape of an oblong spiral shell, they are pierced on 

 all their internal sides with numerous perforations, through 



* This figure shows the branches of the olfactory nerve (o,) passing 1 

 through the thin cribriform plate of the ethmoid bone, and distributed over 

 that membrane. Several of the cells, which open into the cavity, are also 

 seen; such as the large sphenoidal sinus (s,) the frontal sinus (F,) and one of 

 the ethmoidal cells (c.) K, is the nasal bone; P, the palate; and E, the 

 mouth of the Eustachian tube, which leads to the ear. 



j- In this figure, s, is the septum, or partition of the nostrils, on each side 

 of which are seen the sections of the turbinated bones projecting into the 

 cavity; the ethmoid cells (c,) situated between the orbits (o;) and the JLn- 

 trum maxillare (A,) which is another large cavity communicating- with the 

 nostrils. 



