THE SKULL AS A WHOLE 137 



than the roof; it is formed chiefly by the orbital surface of the maxilla; in frnnf. to 

 a small extent, by the orbital prr.>^ nf thp malar and behind, by the superior 

 surface of the orbital process of thp palate . This surface presents at its anterior 

 and internal part, just external to the lacrimal groove, a depression for the attach- 

 ment of the Inferior oblique muscle; externally, the suture between the malar 

 and the maxilla; near its middle, the infraorbital groove; and posteriorly, the suture 

 between the maxilla and palate bone. 



The inner or medial wall (paries medial is) is flattened, nearly vertical, and formed 

 from before backward by the nasal process of the maxilla, the lacrimal. os planum 

 of the ethmoid, and a small part of the body of the sphenoid. This surface pre- 

 sents the lacrimal groove and crests of the lacrimal bone, and the sutures connect- 

 ing the lacrimal with the maxilla, the ethmoid with the lacrimal in front, and the 

 ethmoid with the sphenoid behind. 



The outer or lateral wall (paries lateralis) is directed forward and inward, and 

 is formed in front by the orbital process of the malar bone: behind, by the orbital 

 surface of the greater wing of the sphenoid. On it are seen the orifices of one or 

 two malar canals, and the suture connecting the sphenoid and malar bones. 



Of the angles, the superior external is formed by the junction of the upper 

 and outer walls; it presents from before backward, the suture connecting the 

 frontal with the malar in front and with the greater wing of the sphenoid behind: 

 quite posteriorly is the foramen lacerum anterjus,. or sphenouhil fissure, which 

 transmits the third, the fourth, the three branches of the ophthalmic division of the 

 trigeminal. the abducent nerve, some filaments from the cavernous plexus of the 

 sympathetics, the orbital branch of the middle meningeal artery, a recurrent 

 .branch from the lacrimal artery to the dura, and the ophthalmic vein. The 

 superior internal is formed by the junction of the upper and inner wall, and pre- 

 sents the suture connecting the frontal bone with the lacrimal in front and with 

 the ethmoid behind. The point of junction of the anterior border of the lacri- 

 mal with the frontal has been named the dacryon. This angle presents two fora- 

 mina, the anterior and posterior ethmoidal foramina, the former transmitting the 

 anterior ethmoidal vessels and nasal nerve, the latter the posterior ethmoidal vessels. 

 The inferior external, formed by the junction of the outer wall and floor, pre- 

 sents the spheno maxillary fissure, which transmits the superior maxillary nerve and 

 its orbital branches, the infraorb.it.al vessels, and .the nsrpmlincr I'.riinclips from flip 

 sphenopalatine or Meckel's ganglion. The inferior internal is formed by the 

 union of the lacrimal bone and the os planum of the ethmoid with the maxilla 

 and palate bone. 



The circumference or base of the orbit, quadrilateral in form, is bounded above 

 (margo supraorbital is} by the supraorbital ridge; below (margo infraorbitalis), 

 by the anterior border of the orbital plate of the malar and maxilla; externally, 

 by the external angular process of the frontal and malar bones; internally, by the 

 internal angular process of the frontal and the nasal process of the maxilla. The 

 circumference is marked by three sutures, the frontomaxillary internally, the 

 frontomalar externally, and the malomaxillary below; it contributes to the forma- 

 tion of the lacrimal groove, and presents, above, the supraorbital notch (or fora- 

 men), for the passage of the supraorbital vessels and nerve. 



The apex is situated at the back of the orbit and corresponds to the optic foramen, 1 

 a short circular canal xvhiph transmits the optic nerve and ophthalmic artery. 

 It will thus be seen that there are nine openings communicating with each orbit 

 viz., the optic foramen, sphenoidal fissure, sphenomaxillary fissure, supraorbital 

 foramen, infraorbital canal, anterior and posterior ethmoidal foramina, malar 

 foramina, and the canal for the nasal duct. 



1 Quain, Testut, and others give the apex of the orbit as corresponding with the inner end of the sphenoidal 

 fissure. It seems better, however, to adopt the statement in the text, since the muscles of the eyeball take 

 origin around the optic foramen, and diverge from it to the globe of the eye. 



