THE NASAL CAVITY 513 
chondrium. It is continuous in front with the skin which lines the nostrils, and 
behind with the mucous membrane of the pharynx. It is also continuous at the 
naso-maxillary opening with the very thin and much less vascular mucous mem- 
brane which lines the paranasal sinuses. In the anterior part of the cavity it forms 
prominent thick folds on the lateral wall, which extend from the turbinate bones to 
the nostril. There are usually two dorsal turbinate folds which unite anteriorly. 
Dorsal meatus Septum nasi Lacrimal sac 
Transverse 
facial vessels 
Palatine artery 
Vena reflexa 
Palatine vein 
Buccinator and 
Dep. labii inf. 
Buccinator 
vessels and 
NET VE 
Lingual nerve 
Lingual artery 
Lingual vein 
Mandibular 
duct 
Hypoglossal 
nerve 
Sublingual 
vessels 
External 
maxillary 
vessels 
Digastricus (ant. belly) Parotid duct 
Fic. 456.—Cross-section oF HEAD oF Horsr. Tue Section Passes THROUGH THE MeEpraL CANTHI AND IS VIEWED 
FROM BEHIND. 
1, Mylo-hyoideus; 2, stylo-glossus; 3, hyo-glossus; 4, genio-glossus; 5, lingual process of hyoid bone. An arrow 
points to the naso-maxillary opening. The projecting edge just above the arrow point is the anterior margin of the 
fronto-maxillary opening. 
The upper one encloses a thin plate of cartilage which is continuous with the dorsal 
turbinate bone. The ventral turbinate fold is curved, and encloses an “\~ shaped 
cartilaginous plate which prolongs the ventral turbinate bone; this fold is con- 
tinuous with the alar fold of the nostril, and forms with it the upper margin of the 
entrance from the nostril to the nasal cavity. Below this there is a rounded ridge 
produced by the nasal process of the premaxilla. The mucous membrane of the 
33 ; 
