THE NASA.L 



137 



There may also be found a third parallel fissure above the second fissure, effecting a further 

 separation of the upper concha, so that in these cases there are four distinct conchae on the 

 ethmoid bone alone, viz., suprema, superior, media, and inferior (besides the lowermost or 

 maxillary concha). This condition represents one which is met with in macrosmatic mam- 

 mals in a much more developed form. The most common condition, however, in man, 

 according- to Zuckerkandl, is that with three ethmoidal conchaa, but the middle one, when 

 present, is frequently hidden beneath the superior concha, and thus often escapes observation. 

 Hence the usual description of the ethmoidal conchse as superior and inferior only, the 

 inferior being the one which is spoken of above as the middle turbinal. 



Fig. 156. CORONAL SECTION OP THE NASAL FOSS.E SEEN FROM BEHIND. 



THROUGH THE LAST MOLAR TEETH. (Testut.) 



THE SECTION PASSES 



1, septum nasi ; 2, superior turbinal ; 3, middle turbinal ; 4, inferior turbinal ; 5, posterior 

 ethmoidal cells opening at 5' (on the right side) into the superior meatus ; 6, maxillary antrum, 

 opening at 6' into the middle meatus : the head of the arrow is in the hiatus sermlunaris ; 7, bulla 

 ethmoldalis ; 8, frontal sinuses ; 9, crista galli ; 9', falx cerebri ; 10, cerebral hemispheres; 11, right 

 orbit containing the globe of the eye (surrounded by orbital fat) and its muscles ; 12, great wing of 

 sphenoid ; 13, spheno-maxillary fissure ; 14, fatty tissue of zygomatic fossa ; 15, buccinator muscle ; 

 16, last molar tooth ; 17, vault of palate ; 18, zygoma ; 19, left orbit. 



Besides the ethmoidal fissures which separate the conchse from one another, the superior 

 turbinal is often marked by a distinct groove at its posterior part, which leads backwards into 

 the spheno- ethmoidal recess (fig. 154). 



The superior and middle turbinals are conjoined in front and may be said 

 to spring from the cribriform plate, through which pass the branches of the 

 olfactory nerve. Their free edges slope downwards and backwards, that of the 

 middle turbinal gradually becoming nearly horizontal. The lower margins of both, 

 covered by thick raucous membrane, are free and overhang respectively the superior 

 and middle meatus ; the middle turbinal has also a nearly vertical free border 

 anteriorly, which, together with the adjoining part of the concha, forms an 

 operculum covering the corresponding part of the middle meatus, and concealing 



