THE NOSE 327 



of the air-sinuses which open into it. On the side wall of 

 the middle meatus there is a prominent elevation, termed the 

 bulla ethmoidalis, which contains the middle ethmoidal air- 

 sinuses. At the anterior extremity of the bulla, the middle 

 meatus receives the infundibulum of the frontal sinus. Below, 

 the bulla is limited by the hiatus semilunaris, a groove which 

 receives the openings of the anterior ethmoidal air-sinuses 

 anteriorly and the maxillary sinus (antrum of Highmore) 

 posteriorly. The middle ethmoidal air-sinuses open into the 

 middle meatus at the upper border of the bulla ethmoidalis. 



The superior concha forms the roof of the superior meatus, 

 which receives the openings of the posterior group of the 

 ethmoidal air-sinuses. A small recess, termed the recessus 

 spheno-ethmoidaliS) intervenes between the superior concha and 

 the roof of the nasal cavity and receives the opening of the 

 sphenoidal air-sinus. 



The air-sinuses which open into the nasal cavity are all lined 

 by muco-periosteum, which is continuous with the mucous 

 membrane of the nose. Owing to the proximity of the various 

 orifices to one another, in the middle meatus especially, septic 

 infection originating in one sinus may readily spread to involve 

 the others. 



The outlines of the frontal, maxillary and sphenoidal air- 

 sinuses can all be made out in X-ray photographs, and the 

 condition of the first two can, to some extent, be determined 

 by the process of trans-illumination. 



The Maxillary Sinus (Antrum of Highmore) is placed in the 

 interior of the maxilla. It is present at birth, but does not 

 begin to enlarge until about the seventh year, and after puberty 

 it rapidly increases in size. The orifice by means of which it 

 communicates with the middle meatus is placed high up on its 

 medial wall, and, consequently, when pus collects in the sinus 

 it cannot readily make its escape into the nasal cavity. 



The Frontal Sinuses are placed in the frontal bone above 

 the root of the nose. They are separated from one another 

 by an osseous septum, which is usually deflected to one or 



