50 



THE BONES. 



Fig. 23. 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 

 fibre-cartilaginous framework to the ex- 

 ternal 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 posteriory inferior, or maxillary 

 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 at- 

 tached, by its posterior border, to the ver- 

 tical 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 max- 

 Condyloid foramen ; 2, Section of the illary bone until the horse is about a year 



LONGITUDINAL AND TRANSVERSE SEC- 

 TION OF THE HORSE'S HEAD, SHOW- 

 ING THE FLOOR OF THE CRANIAL 

 AND NASAL CAVITIES, WITH THE 

 MAXILLARY SINUSES. 



parieto-temporal canal ; 3, Occipito- 

 spheno-temporal hiatus ; 4, Carotid 

 notch ; 4', Maxillary notch. a, 

 Supermaxillary fissure ; 6, Cavernous 



Old. 



The meatuses are distinguished into 

 anterior or superior, middle, and posterior 



fissure ; 5, Origin of the supersphe- r inferior. The first passes along the 

 noidal canals. c, Sella turcica ; 6, front of the ethmoidal turbinated bone; 

 Optic fossa; 7, Portion of the the second separates the two turbinated 



crista-galli process; 8, Cribriform i_ -i .. 



plate of the ethmoid bone- 9 p e i- bones > and Presents, near its superior 

 pendicular plate of the same bone ; extremity, the opening communicating 



between the sinuses and the nasal cavi- 



10, 10, Its lateral masses; 11, Inte- 

 rior of the great ethmoidal cell; 12, 



Supe- 



12, Bottom of the maxillary sinuses communicating with the sphenoidal sinuses; 13, ! 

 rior maxillary sinus ; 14, Inferior maxillary sinus ; 14', Superior compartment of the max- 

 illary turbinated bone, forming part of the latter sinus; 15, Section of the supermaxillo- 

 dental canal; 16, Channel of the vomer; 17, Internal process, or point of the premax- 

 illary bone. 



