476 CLARK. 



and softened by standing overnight in water. The drying seems to make 

 the specimen more suitable for the separation of the membranous from 

 the bony structures. It is possible by this method to chip away as much 

 of the bone as is desired, leaving the membranes of the nasal and accessory 

 nasal cavities undisturbed in one continuous piece, the relations of which 

 are then easily determined. A successful preparation is obtained more 

 easily in this manner than after mere preservation in formalin without 

 the drying. In a subject that had been preserved in 50 per cent formalin 

 and dried for two .years, the membranes lining the frontal, maxillary and 

 sphenoidal sinuses, the ethmoidal cells and nasal passages were entirely 

 freed from bone, and a membranous model of all these cavities was ob- 

 tained in one unbroken piece which was mounted on a portion of the 

 occipital bone left undissected. In the negro subject the supraorbital 

 ridges were prominent and the skull, nasal and cheek bones thick. The 

 frontal sinuses of both sides were fairly large, of about equal size and 

 approached the median line where they were separated by a thin lamina 

 of bone. 



The frontal sinus of the left side (see PI. I, fig. 1) is 30 millimeters 

 in its mesial-lateral diameter, 28 millimeters in the saggital, and 12 milli- 

 meters in the antero-posterior diameter. Its lower surface is on a level 

 with the cribiform plate and is 8 millimeters above the fronto-ethmoidal 

 suture. On either side a middle and a posterior ethmoidal cell, 3 which 

 opens into the superior meatus, covers over the entire roof of the orbit 

 behind the frontal sinus. The other ethmoidal cells are small, as are both 

 maxillary sinuses. The sphenoidal sinuses are not excessive in size. The 

 left frontal sinus opens through the nasofrontal duct into the in- 

 fundibulum ethmoidale. Its relations are those usually given for this 

 sinus. The frontal sinus on the right side is in relation to three other 

 frontal cells, the sinus itself representing the second cell. The first 

 frontal cell is situated mesial and below and in close relation to the 

 accessory duct of the sinus. (See PI. I, fig. 1.) The third and fourth 

 are small, narrow cells, 1 and 2 millimeters in diameter, respectively, 

 and lie in close opposition to the posterior surface of the sinus frontalis, 

 between it and the ethmoidal cells which cover over a greater part of the 

 orbit. (See PI. I, fig. 2.) The first, third and fourth frontal cells open 

 into a small vestibule which is a direct continuation of the infundibulum 

 ethmoidale. The frontal sinus (second frontal cell) on its posterior 

 inferior funnel-like surface also communicates with the vestibule through 

 a very short rudimentary nasofrontal duct. It presents a striking 

 peculiarity in the occurrence and course of an accessory ductus naso- 

 frontal. Connection with the infundibulum and the middle meatus is 

 attained only through the common vestibule of frontal cells 1, 2, 3, and 



3 Ethmoidal cells of highest meatus of Killian's eellulae ethmoidates A and B, 

 Plate I, fig. 2. 



