228 THE ESSENTIALS OF HISTOLOGY 



LESSON XLI. 



STRUCTURE OF THE OLFACTORY MUCOUS MEMBRANE 

 AND OF THE EXTERNAL AND MIDDLE EAR. 



1. VERTICAL sections of the olfactory mucous membrane. The sections may 

 be carried either across the middle turbinate bone, after decalcification in 

 0-2 per cent, chromic acid, or across the upper part of the nasal septum. 

 Make a sketch under the low power. Notice the difference in the character 

 of the epithelium in the olfactory and respiratory parts of the membrane. 



2. Teased preparation of the epithelium of the olfactory mucous mem- 

 brane. A piece of the membrane is placed quite fresh in osmic acid (1 per 

 cent.) for a few hours, and is then macerated for two days or more in water. 

 The epithelium is broken up in dilute glycerine ; the cells easily separate 

 from one another 011 tapping the cover-glass. Notice the two kinds of cells. 

 Sketch some of the cells under a high power. 



3. Sections of the external ear (these have been already studied for the 

 cartilage, Lesson XII.) 



4. Sections across the cartilaginous part of the Eustachian tube. Sketch 

 under the low power. 



5. Preparation of the membrana tympani. A piece of the membrane, 

 stained with hsematoxylin, and mounted flat in Canada balsam. 



Determine the composition of the membrane i.e. the several layers com- 

 posing it by focussing carefully with the high power. 



STRUCTURE OF THE OLFACTORY MUCOUS MEMBRANE. 



The olfactory region of the nasal fossae includes the upper and 

 middle turbinate processes and the upper third of the septum. It is 

 covered by a soft vascular mucous membrane of a yellow colour in man. 



The epithelium of the olfactory mucous membrane (figs. 266, 267) is 

 very thick and is composed of long tapering cells, set closely side by 

 side and bounded superficially by a cuticular lamina, through which the 

 free ends of the cells project. The cells are of two kinds : 1. Long 

 narrow spindle-shaped or bipolar cells consisting of a larger part or 

 body (&), containing the nucleus, and of two processes or poles, one (c) 

 straight and cylindrical and extending to the free surface, the other (d) 

 very delicate and varicose, looking not unlike a nerve-fibril and extending 



