THE ORGANS OF SPECIAL SENSE. 



THE NOSE. 



The nose is the peripheral organ of the sense of smell : by means of the pecu- 

 liar properties of its nerves it protects the lungs from the inhalation of delete- 

 rious gases and assists the organ of taste in discriminating the properties of food. 



Seen from below. 



Lower lateral cartilage. 



^Sesamoid cartilages. 



FIGS. 434, 435. Cartilages of the nose. 



The organ of smell consists of two parts : one external, the outer nose ; the 

 other internal, the nasal fossce. 



The outer nose (nasus externus) is the more anterior and prominent part of the 

 organ of smell. Of a triangular form, it is directed downward, and-projects from 

 the centre of the face, immediately above the upper lip. Its summit, or root, is 

 connected directly with the forehead. Its inferior part, or base, presents two ellip- 

 tical orifices, the nostrils or anterior nares, separated from each other by an antero- 

 posterior septum, the columna. The margins of these orifices are provided with 

 a number of stiff hairs, or vibrissoe, which arrest the passage of foreign substances 

 carried with the current of air intended for respiration. The lateral surfaces of 

 the nose form, by their union in the middle line, the dorsum, the direction of 

 which varies considerably in different individuals. The lateral surface terminates 

 below in a rounded eminence, the ala nasi. 



' The nose is composed of a framework of bones and cartilages, the latter being 

 slightly acted upon by certain muscles. It is covered externally by the integument, 

 internally by mucous membrane, and supplied with vessels and nerves. 



The bony framework occupies the upper part of the organ : it consists of the 

 nasal bones and the nasal processes of the superior maxillary. 



The cartilaginous framework consists of five pieces, the two upper and the two 

 lower lateral cartilages and the cartilage of the septum. 



The upper lateral cartilages are situated below the free margin of the nasal 

 bones ; each cartilage is flattened and triangular in shape. Its anterior margin is 

 thicker than the posterior, and continuous with the cartilage of the septum. Its 

 posterior margin is attached to the nasal process of the superior maxillary and nasal 

 bones. Its inferior margin is connected by fibrous tissue with the lower lateral 

 cartilage ; one surface is turned outward, the other inward toward the nasal cavity. 



The lower lateral cartilages are two thin, flexible plates situated immediately 

 below the preceding, and bent upon themselves in such a manner as to form the 

 inner and outer walls of each orifice of the nostril. The portion which forms the 

 inner wall, thicker than the rest, is loosely connected with the same part of the 

 opposite cartilage, and forms a small part of the columna. Its inferior border, 

 free, rounded, and projecting, forms, with the thickened integument and subja- 

 cent tissue and the corresponding parts of the opposite side, the septum mobile 



