THE NASAL CAVITY 509 
the naso-lacrimal duct, is seen when the nostril is dilated; it is situated on the floor 
of the vestibule, anout two inches (ca. 5 em.) from the lower commissure, perforat- 
ing the skin close to its Junction with the mucous membrane. (It is not rare to find 
one or two accessory orifices further back.) 
Structure.—The skin around the nostrils presents long tactile hairs as well as 
the ordinary ones. It is continued around the ale and lines the vestibule. The 
skin 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.—Casr or Lerr Nostrit, Nasav Fria. 452.—Cross-secTion or NASAL REGION or Horse. 
DiverticuLum, AND Nasa VESTIBULE The section is cut about two inches (5 em.) behind the nostrils and a 
or Horse; Dorsat View. little more than half an inch behind the labial commissure. 
N, Nostril; D, diverticulum; 1, super- a, Dorsal meatus; b, middle meatus; c, ventral meatus; d, diver- 
ior commissure of nostril; 2, inferior com- ticulum nasi; e, dorsal turbinate fold; /, ventral turbinate fold; g, 
missure; 3, space occupied by alar fold; 4, prominence caused by venous plexus which extends back on lower part 
groove occupied by dorsal turbinate fold; of ventral turbinate; 1, nasal bone; 2, cartilage of septum nasi; 3, 4, 
5, dorsal meatus. palatine and nasal processes of palatine bones; 5, maxilla; 6, tendon of 
levator labii superioris proprius; 7, part of lateralis nasi muscle which 
ss goes to cartilage of ventral turbinate; 8, 8’, levator nasolabialis; 9, dila- 
shaped somewhat like a com- tor naris lateralis; 10, buecinator; 11, vomero-nasal organ; 12, naso- 
ma, the convex margin being lacrimal duct (wide part)}; 13, lateral nasal artery; 14, 14’, branches of 
m B 5 superior labial artery; 15, palatine artery; 16, labial branches of infra- 
medial (Fig. 453). The eartil- 
orbital nerve; 17, external nasal nerve; 18, hard palate; 19, cheek; 20, 
ages are attached by fibrous superior labial vein. The veins (black) are filled by a natural injec- 
tissue to the extremity of the °"- 
septal cartilage. Each consists 
of an upper, quadrilateral curved plate, the lamina, and a narrow cornu which curves 
ventro-laterally, supporting the medial wing and the inferior commissure, but not en- 
ering 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 
