138 TOPOGRAPHICAL ANATOMY OF THE 



each with its convexity turned forwards. The anterior ridges differ 

 from the most posterior in having the posterior slope much more abrupt 

 than the anterior. The anterior ridges are also better developed and 

 farther apart than the posterior. 



Dissection. — Dissect the hard palate from the bones upon which it 

 lies. Preserve carefully the greater palatine arteries and nerves, which 

 should be secured early as they emerge from the great palatine foramina. 



This dissection discloses the highly vascular deeper layer of the palate. 



A. PALATINA MAJOR. — The Origin of the greater palatine artery 

 from the third part of the internal maxillary, and its entrance into the 

 palatine canal, were observed during the dissection of the structures in 

 the pterygo-palatine fossa (page 127). The artery, accompanied by a 

 nerve (but not by the greater palatine vein), leaves the canal by the 

 great palatine foramen, and proceeds forwards in a sliallow groove on 

 tbe palatine process of the maxilla. 



Near the level of the third incisor tooth, the artery bends round a 

 small projection of the cartilage that fills the palatine fissure. Thence 

 it pursues a curved course to the middle line, where it meets and 

 anastomoses with its fellow artery. The naso-lahial artery (a. naso- 

 labialis) thus produced traverses the incisor foramen and so gains the 

 upper lip, where it divides into right and left main branches. 



N. PALATiNUS MA.TOR. — The greater palatine nerve has been noted 

 previously as the largest of the three terminal branches of the maxillary 

 (page 128). It traverses the palatine canal and groove, in company 

 with the homonymous artery, and supplies branches to the hard palate 

 and gums. 



Dissection. — Preparatory to the removal of the brain, the remains of 

 muscles, &c., should be cleared from the cranial bones. The intact 

 zygomatic arch must be removed with the saw, and the cranial bones are 

 then to be cut away piecemeal with bone forceps down to the level of the 

 root of the zygomatic arches. The removal of the cranial bones must be 

 done very cautiously, so that injury to the dura mater, the fibrous 

 membrane covering the brain, may be avoided. The dura mater is 

 closely applied to the inner surface of the bones, and is particularly 

 adherent along the lines of the sutures and at the base of the cranium, 

 and to projections sucii as the osseous tentorium and the ridge produced 

 by the intruding border of the petrous temporal bone. There may be 

 some difficulty in removing the osseous tentorium, but this should be 

 overcome by gradually stripping the membrane from the bone. 



The occipital bone must be cut away down to the level of the 

 condyles ; that is, the dorsal boundary of the foramen magnum must be 

 removed. It will be found that the dura mater is firmly adlierent to the 

 margins of the foramen. 



Dura mater encephali. — The brain is enclosed in three membranes 

 or meninges, of which the outermost, thickest and strongest is the dura 



