EXTEEIOE, OF THE SKULL. THE ORBITS. 



50 



The foramina in this region, on each side, are the supra-orbital fora- 

 men or notch in the superior margin of the orbit, the infra-orbital 

 foramen below the inferior margin of the orbit, the mental foramen of 

 the lower jaw, and the small irregular foramina of the malar bone. 



The orbits are pyramidal fossa^ irregularly quadrilateral, with their 

 bases directed forwards and slightly outwards, their inner walls being 

 nearly parallel, and their outer walls diverging so as to be nearly at 

 right angles to each other. The roof of each orbit is formed by the 



FisT. 51. 



Fig. 51.— Section of Male Skull of Middle Age, in two planes, one passing 



VERTICALLY THROUGH THE LeFT OrBIT, THE OTHER OBLIQUELY FROil BEHIND THE 



Orbit, backwards and outwards, through the Tympanum and Mastoid Pro- 

 cess. (A. T.) i 



1, section of the frontal bone in the roof of the orbit ; 2, left nasal bone ; 3, nasal 

 process of the superior maxillary bone ; 4, left hichrjTnal bone, and in front the lachi-jTnal 

 groove ; 5, placed on the os plannm of the ethmoid bone, below- the anterior eth- 

 moidal foramen ; 6, is placed below the root of the lesser wing of the sphenoid bone, 

 between the optic foramen and the posterior ethmoidal foramen, and in front of 

 the foramen lacerum orbitale ; 7, orbital plate of the superior maxillary bone inside 

 the infra-orbital groove ; 8, on the orbital plate of the palate bone, in front of and 

 above the spheno-palatine foramen and spheno-maxillary fossa ; 9, the upper extremity of 

 the posterior palatine canal ; 10, the cranial opening of the foramen rotundum— its 

 anterior opening is seen in the spheno-maxillary fossa ; 11, section of the great wing of 

 the sphenoid bone outside the foramen ovale, and in the fossa near- it the anterior opening 

 of the Vidian canal ; 12, placed between the spinous and oval foramina ; 13, on the 

 anterior surface of the petrous bone, near the apex. In front of the figure is seen the 

 sigmoid gi-oove of the internal carotid artery, and below the figure and externally the 

 hiatus Fallopii ; 14, the pituitary fossa, with the anterior and posterior clinoid pro- 

 cesses ; 15, section of the petrous bone above the labyrinth ; two of the semicircular 

 canals are opened ; immediately below is the tympanum. The inner waU is seen with 

 the promontory, fenestra ovalis and p^Tamid in shadow ; forwards near x , the tympanic 

 opening of the Eustachian canal, and backwards, below 16, the opening into the mastoid 

 cells ; 17, left styloid process— that of the right side is seen in perspective below the 

 skull, close by the occipital condjde ; 18, tuberosity of the superior maxilla ; 19, canine 

 fossa ; 20, nasal notch and anterior nasal spine ; 21, inner wall of the antrum seen by 

 the removal of its outer wall ; above the figure is the maxillary process of the inferior 

 turbinateil bone, and over that an in-egular fissure, viz., the opening of the antrum into 

 the middle meatus of the nose, and above that the uncinate process of the ethmoid 

 bone. 



