The Sinus Maxillaris in Man. 323 
merge, and form the cellule ethmoidales anterior, or cellule 
frontales as some call them. From this he concludes that the sinus 
frontalis may continue its development in one of the following 
ways: (1) by extension of the frontal recess (direct method), 
(2) by extension of a frontal cell (indirect method), (8) by ex- 
tension of the frontal recess and a frontal cell, (4) by extension 
of two frontal cells. With these facts kept in mind—allowing 
for further differentiation during development, it is easier to 
understand why the sinus frontalis, in the adult, connects either 
with the infundibulum ethmoidale, with the meatus nasi medius, 
or with both. These embryological facts are of importance in 
connection with adult fronto-maxillary relations. Doubtless 
more work should be done on the development of the nasofrontal 
duct in order to clear up some points in connection with the rela- 
tions existing between the sinus frontalis and maxillaris. J am 
now working along this line and hope to report my findings at 
some future time. | 
Although the pouching to form the recessus frontalis, or what 
may be termed the Anlage of the sinus frontalis, begins during 
the third month of fetal life, as does that of the sinus maxillaris, 
the extension of the sinus frontalis is for a time so small that it is 
usually regarded as wanting at birth. This is in part due to 
the fact that the sinus frontalis is as a rule looked for in the frontal 
or vertical portion of the frontal bone, while the first evidences of 
it are to be sought elsewhere. In fact, according to Lothrop’s 
investigations, the sinus frontalis of the adult does not reach 
the vertical or frontal portion of the frontal bone in about three 
per cent of cases—the only evidences of the sinus appearing in 
the horizontal or orbital portion of the frontal bone. It must, 
however, be said that the sinus frontalis is tardy in its develop- 
ment until after birth; while, on the other hand, the pouch form- 
ing the Anlage of the sinus maxillaris develops more rapidly and 
occupies a definite space in the lateral wall of the nasal fossa by 
the end of the third fetal month (figs. 2, 3). 
By the simultaneous processes of resorption of surrounding 
tissue and the growth of the maxillary pouch, the primitive 
cavity gains more amd more capacity. The pouch soon acquires 
