THE ORGANS OF SPECIAL SENSE. 



organs of the senses (organa sensuum) are five in number those of 

 smell, sight, hearing, taste, and touch. 



THE NOSE. 



The nose is the peripheral portion of the organ of smell (organon olfactus); by 

 means of the peculiar properties of its nerves it protects the lungs from the inhala- 

 tion of deleterious gases and assists the organ of taste in discriminating the prop- 

 erties of food. The organ of smell consists of two parts one external, the outer 

 nose, which projects from the centre of the face, and an internal, the cavum nasi, 

 which is divided by a septum into the right and left nasal fossae. 



THE OUTER NOSE (NASUS EXTERNUS). 



The outer nose is the more anterior and prominent part of the organ of smell. 

 Of a pyramidal form, it is directed downward, and projects from the centre of 

 the face immediately above the upper lip. Its root (radix nasi) is connected 

 directly with the forehead. Its base (basis nasi) presents two elliptical orifices, 

 the nostrils or anterior nares (nares), separated from each other by an antero- 

 posterior septum, the columna (septum mobile nast). The margins of the nostrils 

 are provided with a number of stiff hairs or vibrissae, which arrest the passage 

 of foreign substances carried with the current of air intended for respiration. 

 The point (apex nasi) is the free extremity of the nose. The lateral surfaces of 

 the nose form, by their union in the middle line, the dorsum (dorsum nasi), the 

 direction of which varies considerably in different individuals. The portion 

 of the dorsum over the nasal bones is the bridge. Each lateral surface terminates 

 below in a rounded eminence, the wing or ala nasi, which, by its lower margin 

 (margo nasi), forms the outer boundary of the corresponding nostril. Above the 

 ala is a depression, the alar sulcus. 



Structure. 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 is 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 maxillae (pp. 99 and 104). 



The cartilaginous framework (cartilayines nasi) (Figs. 787 and 788) consists of five pieces 

 the two upper and the two lower lateral cartilages and the cartilage of the septum. 



The upper lateral cartilage (cartilacjo na.n lateral-is) of each side is situated below the free 

 margin of the nasal bone and is flat and triangular in shape. Its anterior margin is thicker than 

 the posterior, and continuous above with the cartilage of the septum. Its posterior margin is 

 attached to the nasal process of the maxilla. 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 cartilage (cartilayo a/am major) is a thin, flexible plate situated immediately 

 below the preceding, and bent upon itself in such a manner as to form the inner and outer walls 



(1081) 



