456 OBSERVATIONS BESPECTING THE NOSE. 



middle of the meatus, and is covered by the middle turbinated 

 bone immediately above it, — a prominence of the cellular 

 structure of the ethmoid bone, which has a curved or semicir- 

 cular figure. Near this prominence, in the same meatus, a 

 groove terminates, which leads from the anterior ethmoid cells 

 and the frontal sinuses. 



From the middle meatus, the membrane proceeds over the 

 inferior turbinated bone, and is reflected round and under it 

 into the lower meatus. It appears rather larger than the bone 

 which it covers ; and therefore the lower edge of the bone does 

 not extend so low as the lower edge of the membrane, which 

 of course is like a fold or plait. The membrane then continues 

 and lines the lower meatus : here it appears less full than it is 

 in the turbinated bone. In this meatus, near to its anterior 

 end, is the lower orifice of the lachrymal duct ; this is simply 

 lined by the Schneiderian membrane, which is continued into 

 it, and forms no plaits or folds that effect the orifice. 



Orifice of the Eustachian Tube. 



Immediately behind each of the nasal cavities, on the exter- 

 nal side, is the orifice of the Eustachian Tube. It has an oval 

 form, and is large enough to admit a very large quill. Its posi- 

 tion is oblique : the upper extremity being anterior to the other 

 parts of the aperture, and on a line with the middle meatus, 

 while the centre is behind the inferior turbinated bone. The 

 lower part of the oval is deficient. This tube is formed poste- 

 riorly by a cartilaginous plate. It is lined by the membrane 

 continued from the nose. 



The cavities of the nose answer a twofold purpose in the animal economy ; 

 they afford a surface for the expansion of the olfactory nerves, and a passage 

 for the external air to the windpipe, in respiration. 



The function of smelling appears to be dependent, to a certain degree, upon 

 respiration. It has been asserted that unless the air passes in a stream 

 through the nose, as in respiration, the perception of odor does not take 

 place ; that in persons who breathe through wounds and apertures in the 

 ■windpipe, the function of smelling is not performed. It is rather in confir- 

 mation of this proposition, that most persons, when they wish to have an 

 accurate perception of any odor, draw in air rapidly through the nose. 



Although the ultimate termination of the olfactory nerves cannot be demon- 

 strated like those of the optic and auditory nerves, it is probable, from the 



