304 HEAD AND NECK 



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 backwards, through the buccinator 

 and the mucous membrane of the cheek, and through the pterygo- 

 mandibular raphe and the side 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 undivided 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 

 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. The deviation is more frequently 

 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 choanae. 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 at 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. 

 That 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). Imme- 

 diately above the orifice of the nostril or anterior aperture 

 of the nasal cavity, the septum shows a slight depression 

 which corresponds to the vestibule of the nose, and forms 

 the medial wall of that subdivision of the nasal cavity. 

 The vestibular part of the partition is clothed with skin, 

 continuous with the external integument ; a number of stiff 

 hairs, termed vibrissa, project from the skin into the cavity. 

 Over the rest of its extent the septum nasi is covered with 

 mucous membrane, which is closely adherent to the subjacent 

 periosteum forming with it a muco- periosteum and it is 



