688 Jacob Parsons Schaeffer. 



The ostia maxillaria 



In this connection little need be said about the ostium 

 maxillare. In the adult it of course is in the position of the 

 primitive sinus maxillaris, i.e., the adult ostium corresponds in 

 position to the evagination of the mucous membrane in the 

 infundibulum ethmoidale for the formation of the anlage of the 

 sinus maxillaris. The formation of the ostium maxillare was, 

 therefore, considered in previous paragraphs and nothing further 

 need be added here. While the ostium maxillare may be primi- 

 tively double, i.e., the anlage of the sinus maxillaris may be 

 represented by a double pouching, it (the ostium) at times becomes 

 duplicated later in life. This latter duplication of the ostium 

 needs to be considered since certain later developmental processes 

 are involved. Very frequently there is also an ostium present in 

 the adult nose which communicates directly between the sinus 

 maxillaris and the meatus nasi medius. This ostium is not pres- 

 ent in the fetus and young child, hence a later developmental 

 process is here involved. In order to complete the consideration 

 of the various developmental stages of the lateral nasal wall it will 

 be necessary brieflj" to consider the duplication of the ostium 

 maxillare and the ostium maxillare accessorium. 



The ostium maxillare accessorium. In a previous paper I re- 

 ferred to the frequent occurrence of an accessory aperture of the 

 sinus maxillaris. In the same article I dwelt briefly on the theories 

 held by several writers as to the genesis of this opening, and stated 

 that I hoped to study the accessory aperture more extensively in 

 the fetus and child, to see whether the opening, after all, at 

 times, did not have an embryological significance. Since then 

 I have had the opportunity of examining a larger number of 

 specimens of the lateral nasal wall of the adult, child, and fetus. 

 . This accessory ostium is, as a rule, situated in the membranous 

 portion of the lateral wall of the middle meatus, a short distance 

 above the cephalic and attached border of the inferior nasal con- 

 cha, at about the junction of its middle and posterior thirds. In 

 some instances the accessory ostium is found immediately dorsal 



