1070 



ORGANS OF SPECIAL SENSE 



Muscles. The muscles are grouped as dilators and constrictors, the latter being 

 comparatively feeble in their action. They are described on pp. 330 and 331. 



The skin covering the external nose is thin and freely movable upon the sub- 

 jacent parts, except at the tip and over the cartilages, where it is much thicker, more 

 adherent, and furnished with numerous large sebaceous glands. At the nares it is 

 reflected into the nasal cavity as far as the limen, where it joins the mucous membrane. 

 The hairs on the skin of the nose are very fine, except in the nares, where they may 

 be strongly developed, and are then known as vibrissae. 



Vessels and nerves. The arteries of the external nose are derived from the external maxil- 

 lary (facial) artery (pp. 523 and 524), the ophthalmic artery (p. 538), and the infra-orbital artery 

 (p. 531). The veins terminate in the facial vein and the ophthalmic vein (p. 662). The 

 lymphatics pass to the submaxillary lymphatic nodes (p. 708). The motor nerves are branches 

 of the facial (p. 979). The sensory nerves are derived from the fifth through the frontal and 

 naso-ciliary branches of the ophthalmic (p. 906) and infra-orbital branch of the maxillary (p. 968). 



The nasal cavity is composed of the two nasal fossse, the bony walls of which 

 have already been described (pp. 101-104) . The nasal fossae extend from the ventral 



FIG. 786. OBLIQUE SECTION PASSING THROUGH THE NASAL FOSSAE JUST IN FRONT OF THE 



CHOAN/E. (Seen from behind.) 



Front wall of left 

 sphenoidal sinus 

 with orifice below 



Orifice of right sphe- 

 noidal sinus 



SUPERIOR NASAL 

 CONCHA 



MIDDLE NASAL CONCHA 



PHARYNGEAL OSTIUM OF 

 TUBA AUDITIVA 



UPPER SURFACE OF 

 SOFT PALATE 



A closed anterior 

 ethinoidal cell 



POSTERIOR ETHMOIDAL 

 CELLS 



RIGHT MAXILLARY SINUS 

 WITH ORIFICE 



INFERIOR NASAL 

 CONCHA 



PHARYNGEAL OSTIUM OF 

 TUBA AUDITIVA 



opening upon the face, the nares, to the dorsal communication with the pharynx, 

 the choanas or posterior nares. Each fossa has a roof, a floor, a lateral and medial 

 wall. 



The medial wall (fig. 767) separates the two fossse. Its framework is formed by 

 the vertical median nasal septum, which is composed of the osseous septum superiorly, 

 the cartilaginous septum intermediately, and of the membranous or mobile septum 

 inferiorly. As already noted, the septum is usually deflected to one side or the other. 

 In the septum, upon each side, just superior to the nasal spines of the maxilla-, 

 there is frequently a minute opening leading superiorly and dorsally and ending 

 in a blind pouch. This cavity is closely related to the vomero-nasal cartilage 

 and is a rudimentary representative of the romero-nasal organ (organ o/ Jacobson), 

 which in some animals is well developed and receives a branch of the olfactory 

 nerve. Inferior and dorsal to its opening another small opening is often seen 

 on the floor of the nasal fossa. This is the mouth of the incisive duct, which leads 

 into the incisive canal for a greater or less distance and may even extend to the 



