THE TURBINATE BONES 69 
form in many places, and covered on both sides with mucous membrane in the fresh 
state. They are arranged in two pairs, dorsal and ventral. 
The dorsal turbinate bone (Os turbinatum dorsale)! is somewhat cylindrical in 
form, but is flattened from side to side and tapers at each end. It is attached to 
the turbinate crest of the nasal bone and the nasal plate of the frontal bone. The 
anterior part is rolled like a scroll one and a half times, thus inclosing a cavity which 
communicates with the middle meatus nasi. The arrangement is best seen on a 
cross-section (Fig. 55). The posterior part is not rolled, but its ventral border is 
attached to the lateral nasal wall, thus helping to inclose a large space which is part 
of the frontal sinus. This cavity is separated from that of the scroll-like part by a 
transverse septum. The medial surface is flattened, and is separated from the sep- 
tum nasi by a narrow interval, the common meatus (Meatus nasi communis). 
Another narrow passage, the dorsal meatus (Meatus nasi dorsalis), separates the 
dorsal surface from the roof of the nasal cavity. The space between the ventral 
surface and the ventral turbinate is the middle meatus (Meatus nasi medius). The 
Nasal Frontal Cranial 
sinus sinus cavity 
Nasal Dorsal nasal 
meatus 
Foramen : - ; : — <4 
incisivum : a a ; 
Sphenoidal 
sinus 
Palatine Hamulus of 
fissure pterygoid bone 
Fic. 44.—Parr or Sacirrat Section oF SKULL or Horse. 
1, Perpendicular plate of ethmoid bone; 2, great ethmo-turbinate; 3, dorsal turbinate; 4, ventral turbinate: 5, 
vomer; 6, middle nasal meatus; 7, ventral nasal meatus; 8, perpendicular part of palatine bone; 9, palatine process of 
maxilla; 10, body of premaxilla; 11, nasal process of premaxilla; 12, palatine process of premaxilla; 13, pterygoid proc- 
ess of palatine bone. Dotted lines indicate septa. 
anterior extremity is prolonged toward the nostril by two small bars of cartilage. 
The posterior extremity is small, and joins the cribriform plate and lateral mass of 
the ethmoid. 
The ventral turbinate bone (Os turbinatum ventrale)? is shorter and smaller 
than the upper one. It is attached to the ventral turbinate crest, and consists, 
like the upper one, of an anterior coiled and a posterior uncoiled portion. 
To express briefly the mode of coiling of the two bones of the same side we may say that 
they are rolled toward the septum and each other. 
The ventral and posterior borders of the posterior part are attached to the 
maxilla, thus helping to inclose a cavity which is part of the maxillary sinus. The 
lower surface is separated from the floor of the nasal cavity by the ventral meatus 
(Meatus nasi ventralis), which is much larger than the other nasal passages. The 
anterior extremity is prolonged toward the nostril by a curved bar of cartilage. 
Development.—Each ossifies in cartilage from a single center. 
_' This bone is also termed the naso-turbinal; it is really a greatly developed first ethmo- 
turbinate. 
? This is also called the maxillo-turbinal. 
