THE HEAD. 



F 



Fig. 34. 



which open, in common, the principal branch of the subsphenoidal canal, the three 

 supra-sphenoidal canals, the Vidian and optic canals, and the orbital opening : 

 this hiatus is surmounted by a thin and sharp bony plate, above which opens 

 the smallest branch of the subsphenoidal foramen ; (e) altogether without the 

 hiatus is remarked a smooth surface belonging to the wing of the sphenoid, and 

 which concurs to form the orbital cavity. 



The internal face is concave from side to side. It shows : 1. On the median 

 line, and from before to behind, a small 

 projection united to the crista-galli ; the 

 optic fossa, elongated transversely in the 

 form of a shuttle, and presenting at the 

 bottom, and on each side, the superior 

 orifice of the optic foramen, a cylindrical 

 canal directed obliquely downwards, for- 

 wards, and outwards, to reach the orbital 

 hiatus ; the supra-sphenoidal or pituitary 

 fossa, also named the sella Turcica, a slight 

 depression, limited behind by a scarcely 

 noticeable transverse projection separating 

 it from the superior channel of the basilar 

 process. 2. On the sides, and in front, the 

 internal surface of the wings, depressed by 

 very superficial digital impressions ; more 

 behind and outwards, a fossa, elongated 

 from before to behind, which lodges the 

 mastoid lobule of the brain ; between this 

 fossa and the sella Turcica, two vertical 

 fissures — an internal, named the cavernous 

 sinus, and an external, wider and deeper, 

 for the passage of a large nervous branch. 

 These two fissures open below, near the 

 junction of the three supra-sphenoidal canals. 

 Two of these, which are very wide, are placed 

 one before the other, and separated only by 

 a slight partition. The superior of these con- 

 stitutes the great sphenoidal fissure {foramen 

 lacerum orhitale) ; the other, the lower, is the 

 foramen rotundum, and opens into the orbital 

 hiatus. The third, very small {foramen pathe- 

 ticiim), is situated outside the great anterior 

 canal, opens above the optic foramen, within 

 the bony mass surmounting the hiatus, and 

 sometimes on the free margin of this lamina. 



Borders. — The superior is a little con- 

 cave, and shows, in its middle, the superior 



extremity of the body, mammillated and articulated with the summit of 

 the basilar process ; on each side, two notches which circumscribe below the 

 occipito-spheno-temporal hiatus {foramen lacerum basis cranii). The internal 

 notch is the narrowest, and from its affording a passage for the internal carotid 

 artery, is called the carotid notch ; it is continued on the external face of the 



POSTERIOR BONES OF THE HEAD OF A 

 FOETUS (horse) AT BIRTH, DISARTICU- 

 LATED AND viewed in FRONT. 



A, Sphenoid bone : 1, ma.xillary notch ; 2, 

 carotid notch ; 3, groove for the passage 

 of the maxillary nerve ; 4, cavernous 

 sinus ; 5, optic fossa ; 6, great wing ; 

 6', unossified portion of the great wing; 

 7, notch for the formation of the orbital 

 foramen. B, Vomer. C, Palatine bone. 

 D, Malar bone. E, Supermaxilla : 8, 

 inferior orifice of the raaxillo-dental 

 canal. F, Premaxillary bone. 



