684 Jacob Parsons Schaeffer. 



find that the ostium of the ethmoidal cell which develops from 

 the meatus suprema I is very often a good point for orientation in 

 determining the presence of a concha suprema I (adult). 



According to Zuckerkandl's series and the series I examined, 

 we should consider the adult ethmoidal region as usually present- 

 ing three ethmoidal conchae rather than two. 



The ethmoid cells and their ostia 



In a previous paragraph on the anlages of the ethmoidal cells 

 we divided them into two groups — anterior and posterior. All 

 those cells that have their ostia openmg inferior to the attached 

 border of the concha nasalis media may be designated as anterior 

 ethmoidal cells ; and those that have their ostia opening superior to 

 the attached border of the concha nasalis media may be designated 

 as posterior ethmoidal cells. The anterior group are in a general 

 way ventral to the posterior group ; however there is at times con- 

 siderable overlapping of the two groups. 



The posterior group of cells. The posterior group of cells com- 

 municate with the meatus nasi superior and suprema I. The latter 

 meatus is present, according to my specimens, in 62.5 per cent of 

 cases; and 75 per cent of the positive specimens have a posterior 

 ethmoid cell opening into this meatus. In some instances the 

 cell which opens into the meatus suprema I is very large and it 

 may encroach upon the lumen of the sphenoidal sinus. Rarely 

 tw^o posterior ethmoidal cells communicate with the meatus 

 suprema I. 



It is a constant condition to have posterior cells opening into 

 the superior meatus. According to my specimens we invariably 

 have a posterior ethmoid cell opening at the superior and ventral 

 extremity of the superior meatus. The latter cell very frequently 

 extends into the body of the concha media, and at times is exces- 

 sively large. In previous paragraphs we spoke of an accessory 

 concha of the superior meatus. We will recall the presence of 

 recesses, inferior and superior to the latter concha — these recesses 

 early giving evidence of cell-anlages. If we carefully look over 

 a series of adult specimens we will in many cases see evidences 



