140 A MANUAL OF ANATOMY 



posterior ethmoidal cells open into the superior meatus, and the 

 sphenoidal sinus opens into the spheno-ethmoidal recess. 



The foramina which perforate the cribriform plate of the ethmoid 

 transmit the filaments of the olfactory bulb, and are arranged in 

 three sets, as follows : a middle set, which are simple perforations, 

 and an external and internal set, which lead into small canals. 

 These canals descend on the inner surface of the lateral mass and 

 corresponding part of the perpendicular plate respectively, branching 

 and opening out as they descend. The nasal slit transmits the 

 nasal nerve and anterior ethmoidal artery. The spheno-palatine 

 foramen leads from the spheno- maxillary fossa, and transmits 

 the internal nerves of Meckel's ganglion and the spheno-palatine 

 artery. 



The anterior nares are the orifices by which the nasal fossae 

 open on the face through means of the anterior nasal aperture. 

 Each naris is semipyriform, and is bounded above by the lower 

 border of the nasal, externally by the nasal notch of the superior 

 maxilla, and interiorly by the premaxillary portion of that bone. 



The posterior nares or choanae are situated at the posterior 

 extremities of the nasal fossae, between the pterygoid processes 

 of the sphenoid, and they communicate in the recent state 

 with the naso-pharynx. They are oblong from above down- 

 wards, and their plane is oblique, being directed downwards and 

 slightly forwards. Each naris is bounded externally by the internal 

 pterygoid plate of the sphenoid, internally by the posterior border 

 of the vomer, which separates the two nares, inferiorly by the 

 posterior border of the horizontal plate of the palate bone, and 

 superiorly by the vaginal process of the sphenoid, ala of the vomer, 

 and sphenoidal process of the palate bone. 



4. The Lateral Region. 



The lateral region (norma lateralis) is formed by portions of the 

 frontal, parietal, sphenoid, temporal, malar, superior maxilla, and 

 inferior maxilla. It is somewhat triangular, with the base directed 

 upwards. The base represents, for the most part, the superior tem- 

 poral ridge, and corresponds with a curved line connecting the 

 external angular process of the frontal with the lateral angle of the 

 tabular part of the occipital. In front and behind it is limited by 

 lines connecting the extremities of the base with the ramus of the 

 inferior maxilla in the vicinity of the angle. This region presents 

 the zygomatic arch, and, from behind forwards, are seen the mastoid 

 process, opening of the external auditory meatus and suprameatal 

 triangle, condyle of the inferior maxilla, lying in the anterior part 

 of the glenoid fossa, eminentia articularis, and the sigmoid notch 

 and coronoid process of the inferior maxilla, the latter lying within 

 the front part of the zygomatic arch. The central point of the 

 orifice of the external auditory meatus is known as the auricular 

 point, and the outer side of the angle of the inferior maxilla is; 



