30 ELEMENTARY PHYSIOLOGY. [l. 



22. Saw through the base of the skull and the face, 

 from the occiput to the nose, a little on one side 

 of the median line. 



The nasal septum will be seen dividing the 

 nasal cavities except posteriorly. Note the 

 anterior and posterior turbinate bones both 

 consisting chiefly of thin folded laminae, pass a 

 bristle through the anterior nasal opening into 

 the nasal cavity, using bone forceps and scissors 

 trace the passage from the nasal cavity through 

 the posterior nasal opening into the pharynx 

 and trachea; note that the posterior turbinate 

 bones are not in the direct course between the 

 anterior nares and the trachea. Cut through 

 the septum nasi dorsally close to the nasal 

 bones, and remove the nasal bones, note that 

 the posterior turbinate bones and the posterior 

 dorsal part of the septum are covered with a 

 yellowish mucous membrane which is thicker 

 than that lining the rest of the nasal cavities ; 

 this is the olfactory part of the mucous mem- 

 brane (Schneiderian membrane). Trace the 

 olfactory nerve forwards from the brain ; it 

 divides into a number of fibres which run to the 

 Schneiderian membrane. 



23. Looking down into the pharynx, observe the 

 epiglottis and the way in which it when pushed 

 backwards folds over the opening to the larynx. 



Put the larynx of the dog into weak spirit for 

 dissection later. (Lesson xxxn.) 



24. Look at the side of the pharynx for the opening 



