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 between the premax- 



illary bones. The posterior border is continuous 

 with the perpendicular plate of the ethmoid l^one.* 

 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 about 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 (Conchse nasales) 

 project from the lateral wall, and divide the outer 

 part of the cavity into three meatuses — superior, 

 middle, and inferior. 



The superior meatus (IMeatus nasi dorsalis) 

 is a narrow passage, l^ounded dorsally by the roof 

 of the cavity, and ventrally by 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 

 between the two turbinal Ijones. It is somewhat 

 larger than the superior meatus, and does not ex- 

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



Parietal 

 lamina of 

 septal car- 

 tilage 



Lamina of 

 alar car- 

 tilage 



Corn u of 

 alar car- 

 tilage 



Fig. .346. — N.\s.\l C.\rtil.\c;es of Horse, 

 Dorsal View. (After EUeuberger- 

 Bauin, Anat. fiir Kiinstler.) 



Inferior 

 meatus 



Superior 



Inferior turbinal „ Ethnio- Septum between 



turbinal Middle ouperior turbinals frontal sinuses 



meatus ^ «.»«/.- o 



meatus 



Fig. .347. — Na8.\l Cavity op Horse, Sagittal Section with Septum Removed. 

 1, Superior turbinal fold; 2, alar fold, containing cartilaginous ijrolongation of inferior turbinal; S, arrow 

 pointitiK to na.so-ma.\illar.v fissure; 4. cranial cavity; 5, .sphenoidal sinus; 0, hamulus of pterygoid bone. The 

 olfactory mucous membrane is sliaded. Dotted lines indicate anterior limit of uncoiled parts of turbinal bones, 

 which incliV'e i)arts of fnmtal and maxillary .sinuses. 



In its posterior part is found the extremely narrow, slit-like interval by which the 



' The septal cartilage is to he regarded as an unossified part of the nicsethmoid. It will be 

 noted that the line of demareation between the bone and the cartilage i.s irregular and varies 

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

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



