314 Jacob Parsons Schaeffer. 
suggestions. I also wish to express my grateful appreciation 
of the abundant material and other facilities placed at my dis- 
posal by the aforementioned departments. To Professor and Mrs. 
Gage, for the loan of embryos from the research collection, I 
wish to express thanks. 
THE EMBRYOLOGY AND EARLY RELATIONS OF THE SINUS 
MAXILLARIS. 
About the tenth week of fetal life the mucous membrane 
in the primitive middle meatus of the nose begins to pouch 
laterally. This pouch represents the Anlage of the sinus maxil- 
laris, which pushes from the originally simple furrow separating 
the maxillo-turbinal (later concha nasalis inferior) and the first 
ethmo-turbinal (later concha nasalis media). 
In order to gain a clearer conception of the location and rela- 
tions of this primary maxillary pouch, and to better interpret 
adult conditions, a brief consideration of the lateral nasal wall, 
of the embryo, is necessary. 
_ During the second month of intrauterine life, before the cavum 
nasi and the cavum oris have become separate cavities, we 
find three swellings on the lateral wall of the nasal fossa 
(maxillo-turbinal, appearing first; ethmo-turbinal, appearing 
next; naso-turbinal—extremely rudimentary in man, appearing 
later) (fig. 1). The maxillo-turbinal corresponds to the adult 
concha nasalis inferior. The naso-turbinal, which is termed by 
Peter, ‘‘der Agger nasi,”’ and by Killian, in conjunction with the 
primitive processus uncinatus, ‘‘der erste Hauptmuschel,”’ per- 
sists in the adult as the agger nasi. The ethmo-turbinal under- 
goes subdivision, and by this division, according to Killian, five 
ethmo-turbinal plates, defined by six grooves, are usually formed. 
EK. Kallius says, ‘‘ Dass alle diese 6 Furchen ausgebildet sind, ist 
selten.’’ Zuckerkandl’s investigations show that three ethmo- 
turbinal plates are the typical number. He says, ‘‘ Drei Siebbein- 
muscheln repriisentieren demnach die typische Faltungsweise 
des Siebbeines.”’ According to the embryos studied for this 
paper, I find that the number of furrows and ethmoidal conch 
varies, but in the specimens examined, four plates are rather 
