THE CELLULE ETHMOIDALES 45 



Seydel observed that an ethmoid cell, having its origin 

 from any given meatus, did not communicate with any cell 

 having its origin from any other meatus. Zuckerkandl 

 took exception to this statement, but certainly every speci- 

 men in this series supports SeydePs view. 



DEVELOPMENT OF THE CELLULE ETHMOIDALES 



In the latter part of the third month of intra-uterine life 

 the conchae nasales assume approximately their definitive 

 outlines, and the corresponding meatuses become well 

 marked. In the meatus medius two accessory folds are 

 distinctly demonstrable, the previously mentioned proc- 

 essus uncinatus and the bulla ethmoidalis, which, by their 

 variations in types and positions, play such an important 

 part in determining the locations of the ostia of the cellulse 

 ethmoidales anterior. In the meatus superior there is 

 often found an accessory fold (Fig. 10), which, though smaller, 

 resembles in general outline the bulla ethmoidalis. In no 

 instance was such an accessory fold found in any of the 

 supreme meatuses. 



The cellulse ethmoidales develop as invaginations of the 

 nasal mucosa, extending into the lateral masses of the 

 ethmoid from the primitive grooves or furrows in the lateral 

 nasal wall. These invaginations, representing the primitive 

 ethmoidal cells, appear in the fourth fetal month as cylindric 

 extensions of the mucosa, in which the epithelial surfaces 

 are in contact. As the diameters of the invaginations in- 

 crease there gradually develop lumina within the cylindric 

 processes (Fig. 13), which, by the sixth fetal month, usually 

 show distinct cell formation. 



