THE NASAL CAVITY 



509 



the naso-lacrimal duct, is seen when the nostril is dilated; it is situated on the floor 

 ot the vestibule, aoout two inches (ca. 5 cm.) from the lower commissure, perforat- 

 mg the skm close to its junction with the mucous membrane. (It is not rare to find 

 one or two accessorj^ orifices further back.) 



Staacture.— The skin around the nostrils presents long tactile hairs as well as 

 the ordinary ones. It is continued around the alse and lines the vestibule. The 

 skm of the diverticulum is thin 

 and usually black, and is cov- 

 ered with very fine hairs; it is 

 provided with numerous seba- 

 ceous glands. The medial wing 

 is supported by the alar cartil- 

 age (Cartilago alaris), which is 



Fig 451. — Cast of Left Nostril, Nasal 

 Diverticulum, and Nasal Vestibule 

 OF Horse; Dorsal View. 

 A^, Nostril; D, diverticulum; 1, super- 

 ior commissure of nostril; 2, inferior com- 

 missure; 3, space occupied by alar fold; 4, 

 groove occupied by dorsal turbinate fold; 

 5, dorsal meatus. 



shaped somewhat like a com- 

 ma, the convex margin being 

 medial (Fig. 453) . The cartil- 

 ages are attached by fibrous 

 tissue to the extremity of the 



Fig. 452. — Choss-section of Nasal Region or Horse. 

 The section is out about two inches (5 cm.) behind the nostrils and a 

 little more than half an inch behind the labial commissure, 

 a. Dorsal meatus; fo, middle meatus; c, ventral meatus; d, diver- 

 ticulum nasi; e, dorsal turbinate fold; /, ventral turbinate fold; (?, 

 prominence caused by venous plexus which extends back on lower part 

 of ventral turbinate; 1, nasal bone; 2, cartilage of septum nasi; 3, 4, 

 palatine and nasal processes of palatine bones; 5, maxilla; 6, tendon of 

 levator labii superioris proprius; 7, part of lateralis nasi muscle which 

 goes to cartilage of ventral turbinate; 8, 8', levator nasolabialis; 9, dila- 

 tor naris lateralis; 10, buccinator; 11, vomero-nasal organ; 12, naso- 

 lacrimal duct (wide part); 13, lateral nasal artery; 14, 14', branches of 

 superior labial artery; 15, palatine artery; 16, labial branches of infra- 

 orbital nerve; 17, external nasal nerve; 18, hard palate; 19, cheek; 20, 

 superior labial vein. The veins (black) are filled by a natural injec- 

 tion. 



septal cartilage. Each consists 



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

 ventro-laterally, supporting the medial wing and the inferior commissure, but not en- 

 tering into the formation of the lateral wing. The lamina causes the projection of the 

 upper part of the medial wing, from which the thick alar fold (Plica alaris) passes 

 backward along the lateral wall of the nasal cavity to join the mucous fold which 



