222 ANIMAL PHYSIOLOGY. 



plate, and two lateral masses. The central plate descends in 

 the middle line from the cribriform plate, and forms the 

 upper part of the nasal septum; while the lower part of the 

 septum is formed behind by another bone, the vomer, and in 

 front is cartilaginous. The lateral masses of the ethmoid 

 form, by two smooth surfaces, part of the inner walls of the 

 orbit, and are hollowed out into air cells, with thin papery 

 walls lined with mucous membrane, and communicating with 

 the nasal fossae. The ethmoidal turbinated bones form part 

 of these lateral masses. The superior one exists only in the 

 hinder half of each mass, and overhangs a space between it 

 and the middle turbinated bone called the superior meatus of 

 the nose, which communicates in front with ethmoidal cells, 

 and has the opening of a space hollowed out of the sphenoid 

 bone, the sphenoidal sinus, opposite it behind (fig. 17). The 

 other turbinated bone of the ethmoid, called he middle 

 turbinated bone, is at the lower part of the lateral mass, and 

 overhangs a gallery between it and the inferior turbinated 

 bone, the middle meatus of the nose. This communicates 

 with a hollow in the upper jaw, the maxillary sinus or 

 antrum, and also, by a passage through the fore part of the 

 lateral mass of the ethmoid, with the frontal sinus, a large 

 hollow in the frontal bone, in the lower part of the forehead. 

 A third gallery or passage, the inferior meatus, lies between 

 the inferior turbinated bone and the floor of the nose; and 

 into it there opens near the front the nasal duct, a canal by 

 which the tears are conveyed from the eye; while, opposite 

 its extremity behind, is the orifice of a communication lead- 

 ing from the ear, the Eustachian tube. 



163. I have thought it better to give the student at once a 

 connected account of the whole interior of the nose, but it 

 must not be supposed that all the structures now described 

 are connected with smell. What is called the" nose, in the 

 more extended sense of the word, has a number of different 

 functions. The nose proper, or feature so called, is simply 

 an organ of expression. The nostrils are of use as the open- 

 ings into the nasal cavities, but the prominence above them 

 is merely ornamental. The nasal cavities are connected 

 with three functions breathing, voice, and smell. Only 

 the ethmoidal part has the filaments of the olfactory nerve 



