512 RESPIRATORY SYSTEM OF THE HORSE 
mass 18 composed, there are three principal and numerous small passages, the 
ethmoidal meatuses (Meatus ethmoidales). 
The choane or posterior nares are two elliptical orifices by which the nasal 
‘avity and pharynx communicate. They are in the same plane as the floor of the 
Parotid External Mandibular 
duct maxillary lymph glands 
vessels 
Fie, 455,—Cross-secTion oF Heap or Horse. 
The section is cut midway between the medial canthus and the anterior end of the facial crest and is a front view. 
1, Septum nasi; 2, 3, 4, dorsal, middle, and ventral meatus nasi; 5, common meatus nasi; 6, cavity of dorsal 
ivity of ventral turbinate bone (7. e., turbinate part of maxillary 
turbinate bone (7. e., turbinate part of frontal sinus) ; 7, 
sinus); 8, maxillary sinus; 9, communication between 7 and 8 over infraorbital canal; 10, naso-lacrimal duct; 11, 
infraorbital nerve and canal; 12, m. levator labii superioris proprius; 13, mouth cavity; 14, palatine artery; 15, fifth | 
upper cheek tooth (posterior part); 16, sixth lower cheek tooth (anterior part); 17, m. buccinator; 18, hard palate; 19, 
vena reflexa; 20, superior buceal glands; 21, buccinator vessels and nerve; 22, alveolar vessels and nerve of mandible; 4 
>, m. hyo-glossus (number placed between two radicles of lingual vein); 26, 
24, mm. genio-glossi 
7, m. mylo-hyoideus; 28, m. genio-hyoideus; 29, lingual nerve; 30, hypoglossal nerve; 31, sub- 
, m. digastricus (anterior belly). The mandibular duct is shown in the fat lateral to the genio-hyoideus 
arked, 
23, lingual artery; 
m. stylo-glossus 
lingual arter, 
but is not m 
together, about two inches (ca. 5 cm.) wide and three to four inches (ca. 8 to 10 
cm.) long. 
The nasal mucous membrane (Membrana mucosa nasi) is thick, highly vas- 
cular, and is, in general, firmly attached to the underlying periosteum and pert | 
nasal cavity, and are separated from each other by the vomer. They are, taken | 
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