FKONTAL SECTIONS OF THE CKANIUM. 



189 



;oncha. Laterally it is related to the maxillary sinus, whilst its floor is formed by the 

 :oncave superior surface of the hard palate. 



The hard palate is arched below, whilst its superior surface is concave upwards on 

 ;ither side of the median crest which 

 ;upports the nasal septum. The sides 

 >f the arch below correspond to the 

 nedial surfaces of the alveolar processes 

 ind fall in line with the lateral walls 

 >f the nasal cavities superiorly. The 

 lummit of the arch lies a quarter of 

 in inch above the level of the floor 

 >f the maxillary sinus. 



The next section (Fig. 177) passes 

 Jirough the pterygo - palatine and 

 temporal fossse inferiorly, and cuts the 

 ;ranial vault about half an inch in 

 I'ront of the bregma. The floor of 

 .he anterior cranial fossa is seen to be 

 brmed by the upper surface of the 

 >ody and small wings of the sphenoid, 

 md is almost horizontal. At the median 

 >lane the sphenoidal sinuses are exposed, 

 -eparated by a thin bony partition, on 

 dther side of which the openings by 

 vhich they communicate with the nasal 

 Cavities are seen. The section passes in 

 ront of the optic foramen, the groove 

 >f which may be seen on the inferior 

 urface of the small wing of the sphe- 

 iioid close to the body, and lays open 

 he superior orbital fissure which here 

 eads forwards into the orbit, and which, 

 nferiorly and laterally, is continuous 

 v r ith the cleft between the maxilla and 

 i he lower edge of the great wing of the 

 phenoid the inferior orbital fissure. 

 ?his also leads into the orbit. 



The nasal cavities, now much dimin- 

 shed in height, are roofed in above by 

 1 he inferior surface of the body of the 

 : phenoid and the alse of the vomer, 

 /hilst the lateral walls are seen to be 

 : ormed by the thin perpendicular parts 

 >f the palate bones, lateral to which 

 he rounded posterior surface of the 

 aaxilla is directed backwards, here 

 orming the anterior wall of the 

 )terygo - palatine fossa the space 

 v r hich lies between the anterior part of 

 he pterygoid process behind and the 

 naxilla anteriorly. As will be seen, 

 he medial wall of this space is formed 

 >y the perpendicular part of the palate, 

 vhich is, however, deficient above im- 

 I nediately below the inferior surface of 

 I he body of the sphenoid. In the in- 

 erval between the orbital process, which ^ oSflLre. 



10 



'20 



FIG. 177. FRONTAL SECTION PASSING THROUGH THE 

 PTERYGO-PALATINE FOSSA. 



1. Depression for arach- 



noideal granulation. 



2. Groove for sagittal sinus. 



3. Crista galli of ethmoid. 



4. Opening of sphenoidal 



sinus into superior 

 meatus of nose through 



10. Zygomatic process of 



maxilla. 



11. Surface of maxilla which 



forms the anterior wall 

 of the pterygo-palatine 

 fossa. 



12. Spheno-palatine foramen. 



spheno - ethmoidal re- 13. Opening of pterygo-pala- 



part of 



tine canal. 



14. Perpendicular 



palate bone. 



15. Pterygoid fossa. 

 surface of great wing 16. Superior meatus of nose. 



17. Middle meatus of nose. 



cess. 



5. Superior orbital fissure. 



6. Part of middle fossa 



formed by cerebral 



of sphenoid. 



7. Zygomatic crest of great 18. Inferior meatus of nose. 

 19. Inferior concha. 



ft , -. " *J. Xi-llCllUl V7L UiLcH llOdULC. 2t\) , .Middle COllCIlil. 



'Ont 01 the section, and the 9. Zygomatic process of 21. Maxillary crest and vomer 

 phenoidal process, which lies behind, temporal. forming nasal septum. 



his forms the spheno-palatine fora- 



nen. Laterally the section has passed through the inferior orbital fissure, which is 

 ontiimous above with the pterygo-palatine fossa. Inferiorly the section passes through 

 he line of fusion of the pterygoid processes with the pyramidal process of the palate 



