OSTIA NASOLACRIMALIA IN MAN 187 



of the region. The concha nasalis inferior is represented as partly 

 dissected away so as to expose for study the ostium of the ductus 

 nasolacrimalis. 



In fig. 5 is represented a fairly common type of ostium. The 

 ductus nasolacrimalis passes through the nasal mucous membrane 

 rather obliquely. The ostium of the duct is rather indefinite and 

 slit-like, and is essentially a potential space. It is guarded by a 

 fold of mucous membrane (plica lacrimalis). The ostium con- 

 tinues caudally towards the floor of the nose in a very shallow, 

 gutter-like depression in the nasal mucous membrane — the depres- 

 sion or gutter becoming shallower and shallower until its ulti- 

 mate disappearance. 



Another very common type of ostium nasolacrimal is repre- 

 sented in figs. 3 and 6. The ostium is located immediately caudal 

 to the attached border of the concha nasalis inferior, i.e., at the 

 most cephalic portion of the meatus nasi inferior. It passes more 

 or less directly through the mucous membrane of the nose and in 

 this respect contrasts strongly with the types represented in figs. 

 5 and 10. The ostium of this type (figs. 3 and 6) is unguarded by 

 folds of mucous membrane, and always presents as a wide, un- 

 guarded, open-mouthed and more or less circular opening. This 

 important type of ostium nasolacrimal, of very common occur- 

 rence, is not even mentioned in many of our texts. It is easily 

 located and probed, and in all respects stands in marked contrast 

 with the slit-like types. This type of ostium is not provided with 

 a 'valve.' 



In fig. 9 is shown a frequent type of ostium. The ostium proper 

 is usually more or less open and somewhat guarded by a plica 

 lacrimalis. Extending from the ostium caudally is a rather deep, 

 gutter-like groove which tends to become deeper as it approaches 

 the floor of the nose. The gutter does not disappear by becoming 

 shallower and shallower as in type fig. 5, but it ultimately termi- 

 nates in a blindly ending pouch in the nasal mucous membrane. 



In fig. 10 is represented the extremely narrow, slit-like type of 

 ostium. It is essentially a potential opening and is well guarded 

 by a plica lacrimalis. It passes very obliquely through the nasal 

 mucous membrane. This type of ostium is usually located with 



