342 Jacob Parsons Schaeffer. 
f. A combination of the above conditions; 
qg. Imperfect dentition. 
The thickness of the sinus walls varies from 5 to 8 mm. and 
down to that of a papery delicacy. The statement that all large 
cavities have thin walls and small cavities invariably thick walls 
does not hold in all cases. The smallest sinus measured in this 
series had the thinnest walls—of a papery delicacy. The small- 
ness of this cavity was in part due to the marked simultaneous 
approximation of the ventral and medial walls. 
The size of the sinus maxillaris is best determined by a series 
of measurements, V1z: 
1. Dorsosuperior diagonal (D.5. D.) 
2. Ventrosuperior diagonal (V.5. D.) 
3. Superoinferior (5. 1.) 
4. WVentrodorsal (V. D.) 
5. Mediolateral (M. L.) 
These several measurements are determined thus (fig. 24): 
Fic. 24. Schematic drawing of the right maxilla. The ventrolateral wall of 
the sinus maxillaris has been removed, thus exposing the base or median wall 
of the cavity. The lines drawn on the base indicate the position of the several 
measurements. 
1, Dorsosuperior diagonal; 2, Ventrosuperior diagonal; 3, Superoinferior; 
4, Ventrodorsal; 5, Mediolateral. 
