ORGAN OF SMELLING. 391 



at the floor of the nostril, which it covers in a smooth even 

 manner. From this it ascends on the septum narium, which it 

 covers also smoothly without forming any fold or duplicature, 

 and adheres so loosely that it may be detached with great fa- 

 cility. Behind, it covers the body of the sphenoid bone< and 

 lines its cell ; in front, it covers smoothly the os nasi and nasal 

 process of the upper maxillary bone, and also the cartilaginous 

 nose. Above, it is reflected upon the cribriform plate of the 

 ethmoid bone, and blocks up all its foramina. At this point, 

 the olfactory nerves seem to terminate on its surface and ad- 

 here very closely to it. 



From the cribriform plate, the Schneiderian membrane passes 

 to the cellular part of the ethmoid, and covers smoothly its an- 

 terior half. But behind, as it passes over the upper spongy 

 bone, a pendulous duplicature is formed along its inferior mar- 

 gin, and is continued beyond the bone, backwards as far as the 

 spheno-palatine foramen. It then lines the upper meatus and 

 the posterior cells of the ethmoid, and is extended upon the 

 convex surface of the middle spongy bone. At the inferior 

 margin of the latter, it forms another loose and somewhat pen- 

 dulous duplication, which does not go beyond the posterior ex- 

 tremity of the bone. The membrane is then reflected into the 

 middle meatus of the nose, and penetrates into the maxillary 

 sinus which it lines completely. The orifice through which it 

 enters, is about the size of a crow-quill ; is variable in its situa- 

 tion, being sometimes in the middle of the meatus, sometimes 

 more forward, and on other occasions higher up and concealed 

 by irregularities, in the conformation of the ethmoid. This ori- 

 fice, which was found to be so large and jagged in the pre- 

 pared bone, is reduced to its present size entirely by the mode 

 of reflection of the mucous membrane over its margins. In 

 front of the latter orifice, beneath the anterior margin of the 

 middle turbinated bone, the mucous membrane is reflected into 

 the anterior ethmoidal cells by one or more foramina, and 

 through the most anterior of these cells into the frontal sinus. 



From the middle meatus, this membrane passes upon the 

 lower turbinated bone so as to cover it, and also to form a loose 

 duplication along its inferior margin; it then lines the inferior 

 meatus of the nose, and is continued on its floor into the part 

 which its description commenced. Under the anterior 



