46 BOXES OF THE HEAD. 



able part of the inner wall of the orbit. The orbital plate articulates 

 in front with the lachrymal, behind with the sphenoid, above 

 with the frontal, and below with the orbital surfaces of the superior 

 maxillary and palate bones. In front of the orbital plate the lateral 

 mass extends forwards, under cover of the lachrymal bone ; and from 

 this part descends the uncinate process, a long thin lamella which curves 

 downwards, outwards and backwards, forming part of the inner wall of 

 the maxillary sinus, and articulating at its extremity with the inferior 

 turbinated bone. 



The internal aspect of each lateral mass forms part of tlie external 

 wall of the nasal fossa, and consists of a thin, uneven plate, connected 

 above with the cribriform lamella, and exhibiting a number of canals 

 and grooves for branches of the olfactory nerve. It is divided at its 

 back part by a channel, directed forwards and upwards from its poste- 

 rior margin to about its middle. This is called the superior meatus of 

 the »056',"and communicates with the posterior ethmoidal cells. The 

 short margin which overhangs this channel constitutes the superior tur- 

 bincded 2)rocess or spongy hone. Below this is a slightly folded margin 

 of greater extent, free in front and behind, the inferior turbinated ^rro- 

 cess or middle spongij bone, which overhangs the middle mecdus of the 

 nose. From the front of the middle meatus a passage, the infundihulum^ 

 is prolonged upwards and forwards through the anterior ethmoidal 

 cells, into the frontal sinus. 



In the separate ethmoid bone the cells are open posteriorly and 

 superiorly, but when the l^one is in connection with the rest of the 

 cranium these cells are closed, above by the frontal bone, and behind 

 by the sphenoidal spongy bones. In the superior margin are twa 

 grooves, which complete with the frontal bone the internal orbital 

 foram^ina. 



The cribriform lamella corresponds in size to the incisura ethmoi- 

 dalis of the frontal bone which it occupies. At the sides of the crista 

 it is depressed into two grooves which lodge the olfactory bulbs ; and 

 it is pierced by numerous foramina, for transmission of the filaments 

 of. the olfactory nerves. The foramina which lie along the middle of 

 each groove, are simple perforations ; the internal and external sets are 

 longer, and are the orifices of small canals which subdivide as they 

 descend on the vertical plate and lateral masses. At the anterior 

 extremity is a small fissure at each side of the crista galli, close to its 

 base, and externally to this a foramen, connected usually by a slight 

 groove with the anterior internal orbital foramen, which transmits the 

 nasal branch of the ophthalmic nerve. 



THE SUPSRIOR MAXILLARY BONE. 



The tipper jaw, maxilla superior, is one of the principal Ijones of the 

 face ; it supports all the teeth of the upper range, and takes part in the 

 formation of the hard palate, the floor of the orbit, and the floor and 

 lateral wall of the nasal cavity. It presents inferiorly a thick ridge, 

 the alveolar process, containing the sockets or alveoli for the roots of 

 the teeth, and a horizontal palate plate ; externally, a convex surface 

 corresponding with the anterior and lateral parts of the face ; supe- 

 riorly, an ascending or nasal process and an orbital plate : and inter- 

 nally, a nasal surface, opening from which is a large cavity or sinus, 



