MORPHOLOGY OF THE SKULL 97 



The ethmoidal canals. — Tlicf^e eouiinence in the suture between the os }ilanuiu and the 

 frontal l)(ine, and traverse the sjiaee between the upper surface of the hiteral mass of the ethmoid 

 and the liorizontal phite of the frontal, to emerge on the eribriform plate ; they are situated 

 outside the dura mater. The anterior foramen transmits the nasal branch of the ophthalmic, 

 which subse(|uently gains the nasal cavity by passing through the nasal slit (ethmoidal fis.sure) 

 by the side of the crista galli. 



The infraorbital canal indicates the line of confluence of the maxillaiy and malar centres of 

 the superior maxilla; occasionally it is completed by the malar; rarely it is incijmplete above, 

 and communicates by a narrow fissure with the orbit. It lodges the infraorbital nerve and 

 artery. 



The spheno-malar foramen is situated in the suture between the malar and the greater 

 wing of the sphenoid (ali-sphenoid) ; it transmits the temporal branch of the orbital nerve an<l 

 a branch of the lachrymal artery. In the adult this Ibramen may be wholly confined to the 

 malar bone. 



The malar canals traverse the malar bone, and indicate the line of confluence of the two 

 chief centres for this bone. The malar twigs of the orbital nerve i.ssue from them accompanied 

 by arterial twigs. 



The spheno-palatine foramen is a deep groove between the orbital and sphenoidal processes 

 of the palate bone, converted into a foramen by the sphenoidal turbinal. It is traversed by the 

 naso-i)alatine nerv(! and arterj' as they enter the nasal from the spheno-maxillary fossa. 



Scarpa's foramina are two minute openings in the meso-palatine suture where it is in relation 

 with the anteri(n' i>alatine fossa. Thej' are traversed by the naso-palatine nerves. 



The pterygo-palatine foramen is situated between the sphenoidal process of the palate bone, 

 the inter'ial pteryg(jid [ilate of the sphenoid, and the sphenoidal turbinal. The pterj'go-palatine 

 nerve and aitery jiass through it. 



The Vidian canal is trumpet-shaped : the narrower end is situated in the sphenotic foramen ; 

 the broader orifice opens on the itosterior wall of the spheno-maxillary fossa. The canal is ]0 

 mm. long ; in the foetal skull it is a chink between the base of the internal jjteiygoid plate, the 

 ali-sphenoid, and the lingula of the sphenoid. The canal is traversed by the Vidian branch of 

 the spheno-palatine ganclion and the Vidian arteiy. 



The posterior palatine canal is a passage left between the maxilla, the vertical plate and 

 tuberosity of the palate bone, and the internal pterygoid plate ; it commences on the hard jialate 

 by the posterior palatine foramen. The descending palatine nerve and ailery traverse this canal. 

 Several f(»ramina ojien from it. In the suture between the vertical plate of the jialate bone and 

 the maxilla, two small oj»enings allow minute nerves to issue for the middle and inierior turbinal.s. 

 In the fissures between the tuberosities of the palate and maxillae, and the pteiygoid plates, the 

 middle and external palatine nerves i.ssue. These foramina are sometimes called accessory and 

 external palatine canals. 



The mandibular or inferior dental canal runs between the dentary and splenial elements of 

 the mandible. The po.sterior orifice of the canal is the mandibular (inferior dental) foramen ; 

 the anterior orifice, the mental foramen, indicates the line of union of the mento-Meckehan and 

 dentary centres. The mandibular nerve and artery enter the canal at its posterior orifice ; the 

 mental foramen allows the mental nerve to escape from the canal accompanied by the mental 

 artery. 



Foramina transmitting the facial nerve and its branches. — The main trunk of the facial 

 enters the internal auditory meatus and traverses the Fallopian canal. In the early embryo the 

 neiTe lies on the petrosal, and is not covered in with bone until the fifth month of foetal life. 

 The terminal orifice, the stylo-mastoid foramen, is situated between the tjTiipanic, tympano- 

 hyal, and epiotic elements of the comjilex temporal bone. 



The ' iter chordae posterius ' is a chink between the squamosal and the tj'nipanic elements, 

 and allows the chorda tympani nerve to enter the tympanum. The fissure of exit for this nerve 

 is the subdivision of tlie Glaserian fissure termed the canal of Huguier, or 'iter chordae 

 anterius.' The Glaserian fissure lies between the tj^mpanic plate and the sf|uamosal. It trans- 

 mits the tympanic branch of the internal maxillary artery, and lodges the slender process of the 

 malleus. 



The spheno-maxillary fissure is situated between the posterior border of the orbital plate of 

 the maxilla and a smooth ridge on the orbital surface of the greater wing of the sphenoid. It 

 transmits the superior maxillary division (second) of the fifth nerve. 



