THE HEAD. 73 



8. Turbinated Bones (Fig. 42). 



The turUnated (or tnrbinal) bones, two on each side, repref5ent two irregular 

 bony columns, wider above than below, compressed laterally, hollowed internally, 

 and lying vertically side by side on the external wall of the nasal fossa, which 

 they divide into three meatuses or passages. 



They are distinguished into anterior and posterior turbinated bones. 



The anterior or superior, also named the ethmoidal, is formed by a very thin 

 plate of compact tissue — fragile and like papyrus, fixed by its anterior border to 

 the internal crest of the nasal bone, and rolled on itself, from before to behind, 

 in the same manner as the cells of the ethmoid bone. Above, it is confounded 

 with the last-named bone, of which it is only, properly speaking, the most anterior 

 volute. At its inferior extremity, it is prolonged by a fibro-cartilaginous frame- 

 work to the external orifice of the nose. 



Its internal cavity is partitioned by a transverse plate into two portions : the 

 superior compartment forms part of the frontal sinus ; the inferior is subdivided 

 by other small lamellae into a variable number of cells which communicate with 

 the nasal cavity. This bone, developed from a single nucleus, is ossified at the 

 same time, and in the same manner, as the ethmoidal cells. Before birth, it is 

 already intimately consolidated with the nasal bone. 



The posterior, inferior, or maxiUarij turbinated bone resembles the first, except 

 in some particulars. Thus, its bony or proper portion is not so long or volu- 

 minous, while its cartilaginous part is, on the contrary, more developed. It is 

 attached, by its posterior border, to the vertical and sinuous crest of the super- 

 maxillary bone, and is rolled from behind to before, or in an inverse direction to 

 the other. It has no connection with the ethmoid, and its superior cavity forms 

 part of the inferior maxillary sinus. It is late in becoming ossified, and is 

 scarcely united in a definite manner to the maxillary bone until the horse is 

 about a year old. 



The meatuses are distinguished into anterior or superior, middle, and posterior 

 or inferior. The first passes along the front of the ethmoidal turbinated bone ; 

 the second separates the two turbinated bones, and presents, near its superior 

 extremity, the opening communicating between the sinuses and the nasal cavities.' 

 The third is situated behind the maxillary turbinated bone, and is confoimded 

 with the floor of the nasal fossa. 



The turbinated bones are essentially disposed to furnish the membrane of the 

 nose with a vast surface of development. This membrane, indeed, covers their 

 entire superficies, and even penetrates the anfractuous cells of their lower 

 compartment. 



Differential Characters in the Turbinated Bones of other Animals. 



A. Ox, Sheep, Goat. — In the Ox (Fig. 43), the ethtuoidal tiirbiiiated bone is very small, 

 and is united to tlie nasal bone by the two borders of its osseous plate ; its internal cavity entirely 

 belongs to the frontal sinus. The maxillary turbinated bone is very deveUjped, and is joined 

 to the bone which sustains it at a later period than in the Horse. Tlie bony lamina of which 

 it is composed, is curved un itself in two different direc'ti(ms — from before to behind by its 

 posterior border, and behind to before by its anterior border. It is fixed to the supermaxillary 

 bone by its middle part, through the medium of a particular bony lamina, and it very incom- 



' The two turbinated bones, in being applied against the excavation on the inner face of the 

 supermaxillary, almost entirely close it, only leaving between them a vertical slit which con- 

 stitutes the opening mentioned above. 



