382 SPECIAL PHYSIOLOGY. 



the pharynx, see Fig. 73. The side of each fossa, next the middle 

 line or septum (Fig. 72, 4, 5), is smooth, but the outer side is more or 

 less convoluted, owing to the presence of three delicate, shell-like bony 

 expansions (Fig. 73), viz., the upper, 2, and middle, 3, turbinated por- 

 tions of the ethmoid, and the lower independent turbinated bone, 4. 

 Below each turbinated bone is a longitudinal recess, named a meatus. 

 These three meatuses, named superior, middle, and inferior, communi- 

 cate with certain cavities, called sinuses, formed in the ethmoid, sphe- 

 noid, frontal, and upper jaw-bones. 



At the anterior nares, the skin which covers the nose externally, is 

 continuous with a lining membrane, called the nasal mucous membrane, 

 pituitary or Sclineiderian membrane, which lines the interior of every 

 part of the nasal fossae, and secretes a fluid naned pituita. This mem- 

 brane, besides being continuous with that lining the pharynx and the 

 Eustachian tubes, is also extended into the several sinuses just men- 

 tioned; moreover, it is prolonged, on each side, through a small canal, 

 leading from the nasal fossae, into the lachrymal sac, and thus becomes 

 continuous with the conjunctiva, or mucous membrane of the eyelids. 



The nasal mucous membrane varies in different regions. First, 

 there is a lower region, in the neighborhood of the nostrils, in which 



Fig. 72. 



Fig. 72. Transverse vertical section across the nasal cavities, opposite to the middle of the hard palate; 

 the anterior section, seen from behind, so that the hinder surface of the upper teeth is seen below. 1, 

 part of inner surface of cranium. 2, projection between the two cribriform plates of the ethmoid bone. 3, 

 cells in the left lateral mass of the ethmoid bone. 4, median septul portion of the ethmoid bone; the nar- 

 row dark space on each side of this, is the olfactory region. 6, the vomer, or bony septum nasi. 6, the 

 middle turbinated portion of the ethmoid. 7, the left turbinatfd bone. 8, section of the malar bone. 9, 

 maxillary sinus, or antrum of Highmore, which communicates with the nasal cavity. (After Arnold.) 



the mucous membrane is firm, pinkish-white in color, provided with 

 fine papillae, and covered with a squamous epithelium, consisting of 

 several layers of cells. Secondly, there is a middle region, in which 

 the mucous membrane is dark-red, soft, provided, in places, with nu- 

 merous little mucous glands, and covered with a cylindrical, or colum- 

 nar ciliated epithelium. Thirdly, there is an upper region, very 

 narrow, from side to side (see Fig. 72), and corresponding with the 

 roof, and the ethmoidal portion of the convoluted sides and septum, 

 where the mucous membrane is pulpy, of a yellowish-brown color, pro- 

 vided, in its upper part, with peculiar short glands, somewhat like the 



