INNERVATION. 



[CHAP. xvi. 



perior maxillary bones, and communicating by narrow apertures 

 with one or other rneatus. 



The nasal fossce are lofty and of considerable depth, but much 

 narrowed in lateral extent by the projection of the spongy bones 

 toward the septum, which they almost touch. They open in front 

 by the nostrils, which, by their horizontal position, direct the 

 air, as it enters, towards the upper region, where the sense of smell 

 is developed; behind, they lead, through a vertical slit on each side, 

 the posterior nares or nostrils, into the upper compartment of the 

 pharynx, above the soft palate, into which the food never penetrates, 

 which is strictly a part of the respiratory tract, and which commu- 

 nicates through the Eustachian tubes with the middle ear. The 

 nostrils, as parts of the countenance, and placed as safeguards at 

 the commencement of the air-passages, are more elaborately organ- 

 ized than the posterior nares, which indeed are simple communica- 

 tions, without any thing remarkable in their construction, except 

 the shelving of the floor of the nose into the upper surface of the 

 soft palate, favouring the gravitation of mucus from the nose into 

 the pharynx. The nostrils have a cartilaginous framework, which 

 keeps them open, unless forcibly compressed. This framework 

 consists of five principal pieces : one in the middle, the septal car- 

 tilage, a, completing the septum in front ; and two on each side, the 

 lateral and alar cartilages, 5, c, forming re- 

 spectively the side of the nose below the 

 nasal bones, and the wing of the nose. The 

 former of these is triangular, and rests against 

 the front edge of the septal cartilage; the 

 latter is thinner and more flexible, and curved 

 upon itself to form the dilatable chamber 

 just within the nostril. Several loose nodules 

 or flakes of cartilage frequently exist in con- 

 nexion with the alar cartilages. The nostrils 

 are further supplied with three pairs of mus- 

 cles; viz. that called by Albinus compressor 

 naris, but which is rather a lateral dilator, 

 the levator and depressor alee nasi. By these, 

 Front vfcw of the cartilages of the orifices are dilated when we sniff the air 



the nose. Above is seen the out- 



the influence 



as we as 

 Lateral cartilage. c, c . Aiar car- o f certain passions. The integuments of the 



tilages, with their appendages. 



After so3imnerrinK. nose are studded with the orifices of sebaceous 



follicles, which are among the largest in the body, and so numerous 

 as to form a thick continous layer under the cutis ; and immedi- 



