NASAL FOSS.E AND SINUSES OF THE NOSE. 31 



The inferior meatus, the largest and most important, 

 lies beneath the inferior spongy bone ; it extends almost 

 the whole length of the fossa ; its lower border, thick 

 and rounded, descends almost to the floor, sometimes 

 converting the meatus into a canal ; anteriorly, where it 

 joins the nasal process of the superior maxilla is the 

 orifice of the nasal duct. 



The opening into it is the nasal duet. This canal 

 extends from the orifice in the meatus to the lachrymal 

 sac (vide Orbital Region), and this orifice is situated 

 about half an inch behind the ascending plate of the 

 superior maxilla, and nearly opposite the centre of the 

 under surface of the lower turbinated bone. It is some- 

 what valvular, owing to the folds of mucous membrane 

 which pass into the aperture and which are continued 

 up the tube. It takes a direction from below, outwards, 

 forwards, and upwards. 



To pass a probe into the nasal duct, the instrument 

 should be first bent into the shape of an italic /, which 

 should be passed first along the floor of the fossa, with 

 its concavity towards the entrance ; the point is next to 

 be pushed gently beyond the ascending plate of the 

 superior maxilla, and kept in close contact with the 

 outer wall ; then it is to be slightly rotated between the 

 fingers, until the point presents upwards and outwards 

 towards the eye; if the handle be now depressed, it 

 should enter the canal. 



The orifice of the Eustachian tube is a valvular aper- 

 ture, situated on the inner surface of the internal ptery- 

 goid plate, and just above the posterior extremity of the 

 inferior turbinated bone. To introduce a sound or probe 

 into it the extremity of the instrument should be bent 

 at an angle of about 60, and passed along the floor of 



