438 



RESPIRATORY SYSTEM OF THE HORSE 



in this situation. The ventral border is thick and rounded ; it lies chiefly in the 

 groove of the vomer, but anteriorly it occupies the space l^etween the premax- 



illary bones. The posterior border is continuous 

 with the perpendicular plate of the ethmoid bone.* 

 The alar cartilages are attached to the anterior 

 extremity by fibrous tissue in such a manner as to 

 allow very free movement — in fact, an actual joint 

 may be found. The ventral part of the cartilage 

 is aliout half an inch (ca. 1 cm.), the middle part 

 about one-tenth of an inch (ca. 2.5 mm.), and the 

 dorsal part about a quarter to a third of an inch 

 (ca. 6 to 8 mm.) in thickness. 



The two turbinal bones (C'onchse nasales) 

 project from the lateral wall, and divide the outer 

 part of the cavity into three meatuses — superior, 

 middle, and inferior. 



The superior meatus (Meatus nasi dorsalis) 

 is a narrow passage, bounded dorsally by the roof 

 of the cavity, and vent rally l)y the superior 

 turbinal bone; its posterior end is closed by the 

 junction of the inner plate of the frontal bone 

 with the cribriform plate and lateral mass of the 

 ethmoid. It transmits air to the upper part of 

 the olfactory region. 



The middle meatus (Meatus nasi medius) is 

 lietween the two turbinal bones. It is somewhat 

 larger than the superior meatus, and does not ex- 

 tend back so far; it ends near the great ethmoturbinal and the ethmoidal meatuses. 



Parietal 

 lamina of 

 septal car- 

 tilage 



Lamina of 

 alar car- 

 tilage 



Cornu of 

 alar car- 

 tilage 



Fig. 340. — N.\sal C.\rtilages of Horse, 

 Dorsal View. (After Ellenberger- 

 Bauni, Aiiat. fiir Kiiiistler.) 



Superior 



Inferior turbinal (. ■ Ethmo- Septuvi beticeen 



turbinal Middle c^upenor turbinals frontal sinuses 



r r ■ V meatus \ meatus 



Inferior \ \ , \ I 

 meatus 



Fig. .347. — Nasal Cavity of Horse, Sagittal Section with Septum Removed. 

 1, Superior turbinal fold; S, alar fold, containing cartilaginous prolongation of inferior turbinal; 3, arrow 

 pointing to naso-maxillary fis.sure; 4, cranial cavity; 5, sphenoidal sinus; 6, hamulus of pterygoid bone. The 

 olfactory mucous membrane is shaded. Dotted lines indicate anterior limit of uncoiled jjarts of turbinal bones, 

 which inclose part.s of frontal and maxillary .sinuses. 



In its posterior part is found the extremely narrow, slit-liko interval l)y which the 



' The septal cartilage is to })e regarded as an unossifiod part of the mesethmoid. It will be 

 noted that the line of demar(!ation between the bone and the cartilage is irregular and varies 

 with age; extensive ossification (or calcification) of the cartilage is commonly found in old animals. 

 The process often results in the formation of calcareous islands in the cartilage. 



