NASAL CAVITIES 389 



branch of the internal maxillary. It arises in the pterygo- 

 palatine ,. fossa and accompanies the infra-orbital nerve. In 

 the face its terminal twigs anastomose with branches of the 

 external maxillary, transverse facial, and buccinator arteries ; 

 in the infra-orbital canal it gives some fine branches to the 

 contents of the orbital cavity, and also the anterior superior 

 alveolar artery which accompanies the nerve of that name, 

 and supplies the incisor and canine teeth, and the lining 

 membrane of the maxillary sinus. 



The infra-orbital vein joins the pterygoid plexus. 



NASAL CAVITIES. 



Dissection. The portion of the mandible which still remains, together 

 with the tongue and larynx, must now be removed from the upper part of 

 the skull. From the angle of the mouth on each side carry the knife 

 posteriorly, through the buccinator and the mucous membrane of the cheek, 

 the pterygo-mandibular raphe, and the lateral wall of the pharynx. The 

 internal pterygoid muscle has been divided already, but it will be necessary 

 to cut the internal carotid artery, the smaller vessels which are still un- 

 divided and the nerves which still connect the pharynx with the skull. The 

 larynx and tongue must be laid aside for future dissection. 



The anterior part of the skull should next be divided into two lateral parts 

 by sawing through it in the sagittal direction close to one side of the nasal 

 septum. As a general rule the nasal septum is not vertical, but deviates 

 more or less to one or other side of the median plane. This deviation is 

 more frequently directed to the right than to the left side. Endeavour to 

 determine the direction which it takes in the skull under observation, 

 by passing a probe into the nasal cavity through the choanoe. The 

 section through the skull should be made close to the concave side of the 

 septum. Begin anteriorly by introducing a knife into the nostril of that side, 

 and carry it upwards through the cartilaginous part of the nose to the nasal 

 bone. Then place the specimen so that the face rests upon the table, and 

 divide the soft palate in the median plane. The section may now be 

 completed by sawing through the hard palate and bony roof of the nasal 

 cavity to the side of the median plane. The dissector should make every 

 effort to preserve the septum of the nose intact. As a general rule the 

 upper concha is partially injured. This is not a very serious matter, as 

 the lateral aspect of the nasal cavity can be studied upon the opposite side 

 when the septum of the nose has been removed. 



Septum Nasi. The nasal septum divides the cavity of 

 the nose into two narrow chambers the right and left nasal 

 cavities. It is not placed accurately in the median plane, 

 but almost invariably shows a bulging or deviation to one 

 or other side (more frequently to the right side). Im- 

 mediately above the orifice of the nostril or anterior aperture 

 of the nasal cavity, the septum shows a slight depression, 



