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 ventrEil. 



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 



Cranial 

 cavity 



A^nsal 

 bone 



13 Sphenoidal 

 sinus 



Hainulus of 

 pterygoid hone 



Palatine 

 fissure 



Fig, 44. — Past of Sagittal Section of Skull of Horse. 

 1, Perpendicular plate of ethmoid bone; 2, grjjat 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. 



1 This bone is also termed the naso-turbinal; it is really a greatly developed first ethmo- 

 turbinate. 



2 This is also called the maxillo-turbinal. 



