HEAD AND NECK IN SECTION 17 



Transverse Sections 



Plate IV. (facing page 14) represents the section across the head 

 immediately in front of or below the orbits. A reference to it will 

 show the intercommunication which exists between the frontal 

 and superior maxillary sinuses, and also between the two divisions 

 of the last-named sinus over the osseous ridges which project into 

 the spaces. 



The outline of the opening of the posterior nares is here 

 somewhat triangular, and the isthmus of the fauces is elongated in its 

 transverse direction, being very narrow from above to below. The 

 section passes through the inferior maxillary bone behind the last molar 

 tooth, and near the angle of the jaw. 



The appearance presented by the lower part of the sinuses as looked 

 at from above is given in Plate V. (facing page 16). 



A very interesting section is that represented in Plate VI. (facing 

 page 18), which is taken immediately at the anterior extremity of the 

 zygomatic ridge of the superior maxillary bone. This section passes 

 through the inferior maxillary sinus a little anterior to the mid-point 

 between its superior (or posterior) and inferior (or anterior) extremities, 

 and the interior of each sinus is visible from the front or below. 

 Looking into it we see the plate of bone which separates the two 

 divisions of each sinus. The inferior maxillary sinus here approaches 

 the quadrilateral in outline, and the nasal chambers are completely sepa- 

 rated from one another by the septum nasi, which is accommodated 

 inferiorly in the cleft formed by the vomer bone. 



In the nasal chamber are the two turbinated bones, the anterior or 

 superior of which is seen arising from its attachment to the nasal bone, 

 whilst the posterior or inferior turbinated bone arises from the nasal 

 aspect of the superior maxillary bone on a level with the middle of 

 the inferior maxillary sinus. 



A vertical transverse section through the left guttural pouch is 



c 



