MUSCLES OF THE NOSTRILS 259 
Origin.—The maxilla, close to the anterior extremity of the facial crest. 
Insertion.—The lateral wing of the nostril. 
Action.—To dilate the nostril. 
Structure—The muscle has a flat tendon of origin, passes between the two 
branches of the levator nasolabialis, and spreads out in the lateral wing of the 
nostril. The lower fibers blend with the orbicularis oris. 
Relations —Superficially, the skin, fascia, and the labial branch of the levator 
nasolabialis; deeply, the maxilla and the nasal branch of the levator nasolabialis. 
Blood-supply.—F acial artery. 
Nerve-supply.—F acial nerve. 
3. Transversus nasi.'\—This is an unpaired, quadrilateral muscle, which lies 
between the nostrils. It consists of two layers. 
Fia. 263.—Nasat AND Superior LasiaL Muscies oF Horse. 
a, a’, Transversus nasi; }, levator labii superioris proprius; 6’, tendon of 6; 6”, common tendon of two 
levatores labii superioris proprii; c,c’, c’’, d, ventral part of lateralis nasi; e, dorsal part of lateralis nasi; f, or- 
bicularis oris; g, levator nasolabialis, a portion of which is removed; h, dilatator naris lateralis (the terminal part of 
which is removed); i, cornu of alar cartilage; k, nostril; k’, upper commissure of nostril; /, nasal diverticulum; m, 
nasal bone. (After Ellenberger-Baum, Top. Anat. d. Pferdes.) 
Attachments.—Superficial layer, the superficial faces of the lamine of the alar 
cartilages; deep layer, the convex edges of the cornua of the same. 
Action.—To dilate the nostrils. 
Structure.—It is composed of transverse fleshy fibers, which blend below with 
the orbicularis. 
Relations.—Superficially, the skin, fascia, and tendinous expansion of the 
levator labii superioris proprius; deeply, the alar cartilages, the extremity of the 
septum nasi, and the palato-labial artery. 
Blood-supply.—Palato-labial artery. 
Nerve-supply.—F acial nerve. 
Lateralis nasi—This is situated along the margins of the naso-maxillary notch, 
and may be regarded as consisting of dorsal and ventral parts. 
The dorsal part (Pars dorsalis m. lateralis nasi)? is a thin layer which lies along 
1 Also called the dilatator naris transversus. 2 Also known as the dilatator naris superior. 
