TEE HEAD. 



91 



Fig. 55. 



4. Ethmoid bone. — In Man, the externnl face of the lateral masses — formed by a very 

 thin lamina, termed the os planum or lamina papyracae — belongs to the internal wall of the orbit. 



5. Sphenoid hone. — Tliis is distinguished, in Man, into a body and four wings — two large 

 and two small. 



The inferior surface of the body offers nothing remarkable, except the presence of a conical 

 prolongation named the beak (rostrum) of the sphenoid. The external face of the greater 

 wings forms part of the temporal fossa, as also tlie external wall of the orbit. At the union 

 of the wings with the body, are detached two bifid 

 pterygoid proci-^scs; their internal branch represents 

 the pterygoid bones of animals. There is no sub- 

 sphenoidal canal. 



The two lesser wings are very thin and triangular, 

 and .visible only on the superior surface of the bone ; 

 they constitute the processes of Ingrassias. 



On the internal face of tlie bone are found: (1) 

 a deep pituitary fossa, limited by four clinoid pro- 

 cessi's; (2) an optic fossa, shallow, showing very 

 short optic canals transformed into foramina ; (:->) f lie 

 sphenoidal fissure, whicii replaces the great super- 

 eplienoidal canal in the Horse; (4) the great fciranien 

 rotundum ; (5) the internal face of the wings, much 

 excavated ; (6) the foramen ovale, which transmits 

 the inferior maxillary nerve ; (7) the small foramen 

 rotundum that lodges the spheuo-spinous artery. 



6. Temporal bone. — In the squamous portion of 

 the temporal bone of Man, the zygomatic process only 

 rests on the malar bone, as in Ruminants. The glenoid 

 cavity is concave in every sense, and divided into two 

 parts by an opening named the Ji^sura Glaseri ; the 

 anterior portion oidy is articular— tlie posterior, lying 

 against the external auditory canal, does not belong 

 to the articulation ; it corresponds to the supra-con- 

 dyloid eminence of the Horse. The tuberous portion 

 is consolidated with the squamous. It is divided into 

 a mastoid and a pyramidal portion ; the latter com- 

 prises, in its turn, the petrous and tympanic portions. 

 The mastoid portions correspond to the mastoid pro- 

 cess, mastoid protuberance, and superior border of the 

 petrous bone in the Horse. It presents a rugged 

 mastoid process. Above this is the mastoid canal ; 

 and aliove and behind it, the digastric gmove — the 

 pyramid forming a considerable projection in the 

 interior of the cranium. The styloid process or bone 

 is altogether separate from the other pieces of the 

 hyoid, and in the adult is consolidated with the tem- 

 poral bone. 



7. SupermaxilJa. — In Man the premaxilla is no 

 longer found independent, the centre which forms it 

 coalescing with the supermaxillary bone. 



The supermaxilla of man cuueurs, for the greater 

 part of its extent, to form tlie floor of the orbit ; it 



is also divided into three faces : an external or facial, a superior or orbital, and an internal 

 or naso-palatine. The external face presents, from before to behind: (1) a. small fo.ssa, into 

 which is inserted the inyrtilorm muscle ; (2) the infra-orbital, or canine fossa, showing the 

 inferior orifice of the infra-orbital canal; (3) a crest corresponding to the maxillary spine of 

 Solipeds : (4) the alveolar tuberosity. This face carries, in front, a prolongation that forms the 

 ascending process, also named, because of its relation, the tionto-nasal process. The superior 

 or orbital face offers a fissure which precedes the infra-orbital canal, and, outwards, the malar 

 process. The internal face is divided by the palatine process. It shows, in front, the half of 

 the anterior nasal spine and a groove which participates in the formation of the incisive canal. 



8. Palatine bone. — The palatine bone of Man is formed of two osseous laminae —one horizontal, 

 the other vertical— which are joined at a right angle. The first part presents : one-half of the 



EXTERNAL OR r.ASILAR SFRFACE OF 

 THE BASE OF THE HUMAN SKULL. 



1, 1, The bony palate; 2, incisive, or 

 anterior palatine foramen; .3, pala- 

 tine process of palate bone, with the 

 posterior palatine foramen ; 4, palate 

 spine with transver.se ridge ; 5, vomer ; 

 6, internal pterygoid palate ; 7, hca- 

 phoid fossa; 3, external pterygoid 

 plate, with fossa ; 9, zygomatic fossa ; 



10, basilar process of occipital bone ; 



11, foramen magnum; 14, glenoid 

 fossa; 15, meatus auilitorius exter- 

 nus ; 16, fiirainen lacerum anteriiis ; 

 17, carotid foramen of left side; 18, 

 foramen lacerum posterius, or jugular 

 foramen; 19, styloid process; 20, 

 stylo-mastoid foramen, with jugular 

 tubercle and digastric fossa ; 21, mas- 

 toid process; 22, occipital bone ; 23, 

 posterior condyloid fossa. 



