Lateral Wall of the Cavum Nasi in Man. 679 



the duct depending upon the cell from which the sinus developed 

 and upon the degree of development and the disposition of the 

 other anterior ethmoid cells. On the other hand, when the frontal 

 sinus develops by a direct extension of the frontal recess there will 

 in all likelihood be no true nasofrontal duct. Occasionally the 

 adult frontal sinus has two nasofrontal ducts. This is explained 

 by the fact that the sinus at times develops from two anterior 

 ethmoid cells. In many instances the frontal sinus is in reality 

 nothing other than an extensively developed anterior ethmoid 

 cell. 



The cellulae ethmoidales 



The ethmoidal cells all develop from preformed furrows or 

 recesses. They are nothing but extensions from some of the 

 meatus nasi directly, or from the accessory recesses and furrows 

 of the meatus nasi medius and superior. From the frontal fur- 

 rows of the recessus frontalis, and from the furrows of the descend- 

 ing ramus of the meatus medius, the anterior group of ethmoid 

 cells develop. From the ventral and superior extremity, and 

 the superior and inferior recesses of the meatus superior ; and the 

 meatus suprema I, the posterior group of ethmoid cells develop. 

 The anterior group have, therefore, their ostia opening inferior 

 to the attached border of the concha nasalis media, and the pos- 

 terior group have their ostia opening superior to it. The so-called 

 middle group of ethmoidal cells are thus classed with the anterior 

 group, and the term 'middle ethmoidal cells' is dropped. This 

 I think is a better classification because the cells of the bulla are 

 closely associated with the cells of the frontal recess. 



The lateral masses of the ethmoid bone and its appendages, 

 such as major and accessory conchae, are primitively solid struc- 

 tures. Later, however, the lateral masses become more or less 

 honey-combed or labyrinth-like by the developing ethmoidal 

 cells. The ethmoid cells, while primarily confined to the lateral 

 ethmoidal masses, frequently extend beyond these limits into 

 the concha media, the processus uncinatus, and the agger nasi. 

 The bulla ethmoidalis is practically always shell-like due to a cell 

 or cells. Anterior ethmoid cells may develop far into the frontal 



