184 J. PARSONS SCHAKFFEK 



position of the ostium nasolacrimal. It is located from 15 to 

 20 mm. dorsal to the limen nasi, and from 30 to 40 mm. dorsal to 

 the naris (anterior naris). Considerable variation also exists in the 

 cephalo-caudal plane: It is frequently found in the most cephalic 

 portion of the meatus nasi inferior, immediately caudal to the 

 attachment of the concha nasalis inferior to the lateral nasal wall. 

 Again we see specimens in which the ostium is 10 mm. (rarely 

 more) caudal to the above point. Between these two extremes 

 we, of course, encounter ostia at various distances caudal to the 

 attached border of the concha nasalis inferior (figs. 4. 6, 9 and 11). 



DUPLICATION OF THE OSTIUM 



The ostium nasolacrimal is usually a single opening. We, 

 however, encounter specimens in which the opening is duplicated. 

 A triplicity of the ostium was encountered in the series studied. 

 Fig. S represents a specimen in which the ostium was duplicated. 



TYPES OF OSTIA 



The unqualified statements found in some of our text-books, 

 that the ductus nasolacrimal at the point of communication with 

 the meatus nasi inferior, is provided with a valve (plica lacrimalis 

 or the so-called valve of Hasner) is certainly at variance, in many 

 instances, with the real anatomic condition. A study of this 

 ostium or communication in a large series of cadavers at once 

 demonstrates that there is no unvarying typical form but that, 

 on the other hand, we are dealing with several normal anatomic 

 types of ostia nasolacrimalia. In order to make more compre- 

 hensible the several types of ostia encountered in this study it 

 may be well to refer to the illustrations, figs. 1 to 1 1 , in the accom- 

 panying plate. The drawings were made from actual dissections 



Pigs. 1 to 11 Drawings of actual dissections illustrating the various types of 

 ostia nasolacrimalia encountered in this study. The reader is referred to the text 

 lor a further consideration of them. The concha nasalis inferior is represented as 

 partly cut away so as to expose for study the manner of communication between 

 the ductus nasolacrimal and the meatus nasi inferior. X ;-'. 



