54 



THE BONES. 



orbital foramen is formed by the frontal bone only. There is no mortise for the union of the 

 frontal with the sphenoid bone ; and the frontal sinuses are prolonged into the parietal. The 

 frontal bone articulates with the superior maxillarie.s (Fig. 28). 



D. Carnivora. — In the Carnivora, the external face of the frontal bone presents in its 

 middle a more or less deep depression. The ori)ital arch is incomplete, and there is no supra- 

 orbital foramen or mortise on the inner face. 



superior maxilLiry bones 



anterior bones of the head op a fcetus 

 (horse) at birth, disarticulated, and 

 viewed from behind. 



It unites with tht 

 (Fi-. 29). 



E. Rabbit. — In this animal the frontal 

 bone is long and narrow, and the orbital 

 process is thin, elevated, and directed upwards 

 and backwards, but it does not reach the 

 zygomatic bone, and is deeply notched at its 



4. Ethmoid Bone (Fig. 33). 



The ethmoid bone, deeply situated 

 m the limit between the cranium and 

 the face, is enclosed between the frontal, 

 the sphenoid, the vomer, the palatine, 

 and the supermaxillary bones. It is 

 composed of three portions — a jjer- 

 pendicular plate, and two lateral masses. 



The Perpendicular Lamina of 

 THE Ethmoid Bone. — Situated in the 

 mesian plane, and flattened on both 

 sides, this bone presents tu'o faces, a 

 left and right, and four borders. 



Faces. — The faces, covered by the 



., Occipital bone : 1, condyle ; 2, condyloid 

 foramen ; 3, styloid process ; 4, summit of 

 basilar process. B, Parietal bone : 8, j)arie- 

 tal protuberance; 9, channel which concurs 

 to form the parieto-temporal canal. C, Fron- 

 tal bone: 10, transverse crests separating 

 the cranial from the facial portion of the 

 bone; 11, frontal sinuses; 12, notch on the 

 lateral border occupied by the wing of the 

 sphenoid bone ; 13, notch for the formation 

 of the orbital foramen ; 14, summit of the 

 orbital process ; 15, supra-orbital foramen. 



D, Perpendicular lamina of the ethmoid bone. 



E, E, Lateral masses of the ethmoid bone : 

 16, the great ethmoid cell. F, Squamous 

 portion of the temporal bone : 17, Supra- 

 condyloid process ; 18, channel for the forma- 

 tion of the parieto-temporal canal. G, Pet- 

 rous portion of the temporal bone : 5, 

 mastoid process ; 6, internal auditory hiatus ; 

 7, opening for the Eustachian tube into the 

 tympanum, h, Lachrymal bone. I, Nasal 

 bone. J, Superior turbinated bone. 



pituitary membrane, present, posteriorly, small sinuous crests ; elsewhere they are 

 smooth. A very narrow interval, constituting the bottom of the nasal cavities, 

 separates them from the lateral masses. 



Borders. — The superior border looks towards the centre of the cranial cavity, 

 and constitutes what is called the ethmoidal ridge, or crista-galli ^wocess. It is 



