THE NASAL CAVITY 



437 



posterior part of the diverticulum the skin is thin and usually black, and is covered 

 with exceedingly fine hairs; it is provided with numerous sebaceous glands. The 

 inner wing is supported by the alar cartilage (Cartilago alaris), which is shaped 

 somewhat like a comma, the convex margin being direct medially. The cartilages 

 are attached by fibrous tissue to the extremity of the septal cartilage. Each consists 

 of an upper, quadrilateral curved plate, the lamina, and a narrow comu which 

 curves downward and outward, supporting the inner wing and the lower com- 

 missure, but not entering into the formation of the outer wing. The lamina causes 

 the projection of the upper part of the internal wing, from which the thick alar fold 

 (Plica alaris) passes backward along the external wall of the nasal cavity to cover 

 the cartilaginous prolongation of the inferior turbinal bone. This fold separates the 

 true from the false nostril. The extremity of the cornu usually causes a slight 



Fic. 344. — Nostrils of Horse. 

 a. Diverticulum nasi (shown as if distended); b, 

 philtrum; c, false nostril; d, true nostril; e' , prominence 

 caused by lamina of alar cartilage; e", prominence over cornu 

 of same; /, external wing of nostril; q. internal wing; h, 

 lower commissure; /, orifice of naso-lacrimal duct. (Ellen- 

 berger-Baum, Anat. d. Haustiere.) 



Fig. 345. — Cross-section of Narial Region of 

 Horse. 

 /, Xasal bone; 2, tendon of levator labii su- 

 perioris proprius; 3, external nasal nerve; 4, nasal 

 diverticulum; 5, outer wall of 4! 6, dilatator naris 

 inferior; 7, levator nasolabialis + dilatator naris 

 lateralis; S, maxilla and premaxilla; 9, naso-lacrimal 

 duct; 10, 11 , chief branches of sujjerior labial nerve, 

 with superior labial artery at their inner side; 13, 

 nasal cavity; 13, superior turbinal fold; 14, inferior 

 turbinal fold, inclosing cartilaginous prolongation of 

 inferior turbinal bone; 15, venous plexus; 16, sep- 

 tum nasi; 16', parietal cartilage; 17, vomero-nasal 

 organ (of Jacobson) ; 18, venous plexus of palate; 

 19, buccinator; 2.0, skin; 33, anterior nasal nerve; 

 24, palatine process of premaxilla. (After Ellen- 

 berger-Baum, Top. Anat. d. Pferdes.) 



projection of the skin a short distance 

 behind and below the lower commissure. 



The muscles of the nostrils have been 

 described. 



Blood-supply. — Palato-labial, superior 

 labial, and lateral nasal arteries. 



Nerve-supply. — Trigeminal and facial 

 nerves. 



The nasal cavity is divided into two symmetrical halves by the median septum 

 nasi. The osseous part of the septum (Septum osseum) is formed behind by the 

 perpendicular plate of the ethmoid and below by the vomer. A few ridges on 

 the former correspond to the ethmoidal meatuses. The major part of it, how- 

 ever, is formed by the septal cartilage (Cartilago septi nasi). The surfaces of the 

 cartilage are marked by faint grooves for the vessels and nerves which course 

 over it. The dorsal border is attached along the frontal and nasal sutures, and 

 extends beyond the apices of the nasal bones about two inches (ca. 5 cm.). 

 From this border a thin, narrow plate, the parietal cartilage (Cartilago parietalis) 

 curves outward for a short distance on either side. Near the nostrils these plates 

 are somewhat wider, partially making good the defect in the bony roof of the cavity 



