60 BOXES OF THE HEAD. 



orbital process of the frontal and the small wing of the sphenoid 

 bone ; the floor by the orbital processes of the malar and superior 

 maxillary bones, and by the small orbital surface of the palate bone 

 at the back part ; the inner wall by the ascending process of the 

 superior maxillary, the lachrymal, the ethmoid, the sphenoid, and 

 sometimes the palate bone ; and the outer Avall by the orbital surfaces 

 of the malar bone and great wing of the sphenoid. The sphenoidal 

 fissure (foramen lacerum orbitale), at its inner extremity, occupies the 

 apex of the orbit, while its outer and narrower part lies between 

 tlie roof and the external wall. The foramen opticum is internal and 

 superior to the sphenoidal fissure. In the angle between the external 

 wall and the floor is the splmio-maxillarij fissure, bounded by the 

 sphenoid, palate, superior maxillary, and malar bones, and leading 

 into the spheno-maxillary fossa at its back part, and the zygomatic fossa 

 at its fore part. Passing forwards from the margin of the spheno- 

 maxillary fissure is the commencement of the infra-orbital canal, groov- 

 ing the posterior part of the floor of the orbit. On the inner wall in 

 front is the lachrymal groove, formed by the superior maxillary and 

 lachrymal bones, and leading into the nasal duct : further back, 

 between the ethmoid and frontal bones, are the anterior and posterior 

 etlmioidal foramina; on the roof at its anterior margin, i^ the 

 supra-orbital foramen or notch ; within the external angular process is 

 the fossa for the lachrymal gland ; and in the outer wall are one or two 

 minute foramina which perforate the malar bone. 



The lateral region of the skull presents in a horizontal line from 

 behind forwards the mastoid process, the external auditory meatus, the 

 glenoid fossa, with the condyle of the lower jaw, and the zygomatic or 

 malar arch, formed by the zygomatic process of the temporal bone and 

 the posterior part of the mahir. When the head of the lower jaw is in 

 the glenoid cavity, the coronoid process lies internal to the malar arch. 

 The upjier part of the space bridged over by this arch is called the 

 temporal fossa, the lower part the zyijomaiic fossa, the line of division 

 being the rough ridge which divides the external surface of the great 

 wing of the sphenoid bone into an upper and lower portion. The 

 temporal fossa is occupied by the temporal muscle; it is bounded 

 superiorly by the temporal ridge ; and the frontal, parietal, sphenoid 

 and malar bones take part in its formation. The zygomatic fossa is 

 occupied in part by the external pterygoid muscle ; its wall is formed 

 internally by the external pterygoid plate, superiorly by the lower part 

 of the gi'eat wing of the sphenoid bone, and anteriorly by the superior 

 maxillary. Inferiorly the external pterygoid plate comes nearly into 

 contact witli the superior maxillary bone, but is almost always separated 

 from it by a thin portion of the pyramidal process of the palate bone ; 

 superiorly, it is divided from ithy the pfei'ijr/o-maxillary fissi(7-c, a vertical 

 opening, which leads into the spheno-maxillary fossa, and which is con- 

 tinued above into the outer extremity of the horizontal sphcno-maxillarj' 

 fissure opening into the orbit. 



The spheno-maxiUanj fossa is the space which lies in the angle 

 between the pterygo-maxillary fissure and the inner part of the spheno- 

 maxillary fissure. It is bounded posteriorly by the external pterygoid 

 process and lower part of the anterior surface of the great wing of the 

 sphenoid bone, anteriorly by the superior maxillary bone, and internally 

 by the vertical plate of the palate bone. Into this narrow space five 



