The Sinus Maxillaris in Man. Soi 
meatus nasi medius, immediately superior and lateral to the free 
border of the processus uncinatus (fig. 4). This is the Anlage of 
the bulla ethmoidalis. The slit-like space existing between the 
free border of the processus uncinatus and the bulla ethmoidalis 
is the primary hiatus semilunaris. Through this slit the infun- 
dibulum ethmoidale communicates directly, and the primitive 
sinus maxillaris indirectly, with the meatus nasi medius. 
Palatum 
Fic. 4 (X6.6). Drawing of a frontal section of the nose of an embryo aged 
120 days. The section is 7.25 mm. from the tip of the nose. Note that on one 
side the section is in the region of the ostium maxillare, on the other it is dorsal 
to it; also the fusion between the processus uncinatus aad a frontal concha. 
Inf. Eth-, = infundibulum ethmoidale; 0. M., = ostium maxillare; S. Max., = 
sinus maxillaris; Os., = developing bone; F. Cr. Ant., = fossa cranii anterior; 
B. Eth.,=bulla ethmoidalis; H. Sem., = hiatus semilunaris; Proc. Unc., = pro- 
cessus uncinatus. 
Killian subdivides the uneven thickening on the lateral wall 
of his “Ramus decendens der ersten Hauptfurche” into small pro- 
jections with very shallow intervening furrows. The projections 
are his “‘absteigende Nebenmuscheln”’, and the furrows the ‘‘ obere 
und untere Zwischenfurchen”’ of the first furrow, or the primitive 
meatus nasi medius. He concludes that the bulla is formed by 
