n8 



The sections were cut in a direction parallel to the long axis, stained 

 in hsematoxylin and acid fuchsin, and are now in oil of bergamot. 

 Mount in balsam. 



The cochlear canals were opened on one side so that 

 the hardening fluid might penetrate more easily. Study 

 first under low power. Observe the bony axis or modeolus 

 about which the cochlear canal is spirally wound. Sections 

 of it are seen on either side of the modeolus. The coch- 

 lear canal is divided into two portions by the lamina 

 spiralis, a bony crest attached to the modeolar wall of the 

 canal, and the basilar membrane extending from the lamina 

 spiralis to the ligamentum spiralis. The upper portion of 

 the canal is the scala vestibuli, the lower the scala tympani ; 

 they are lined by endothelial cells. A triangular canal, the 

 cochlear duct or scala media, is cut off from the scala vesti- 

 buli by Reissner's membrane. In the cochlear duct resting 

 on the basilar membrane is. found the organ of Corti, in 

 which the following parts are to be distinguished : The 

 pillars of Corti, arranged in the form of an arch ; the inner 

 and the three or four outer hair cells; Deiter's cells sup- 

 porting the outer hair cells ; peripheral to the organ of 

 Corti are Hensen's cells, in these fat granules are found in- 

 the guinea pig. Note the membrana tectoria resting on 

 the organ of Corti. Observe the spiral ganglion in the 

 lamina spiralis; from this nerve fibres pass toward the 

 organ of Corti, and make connection with the hair cells. 

 They may be seen passing through the tunnel of Corti. 



Sketch under low power the entire section, also under 

 high power a cochlear duct with the organ of Corti. 



(f) Olfactory Membrane (Teased). 



The olfactory membrane of a dog was fixed and macerated in 

 YJ, % 'osmlc acid. Place a small piece of the macerated tissue 

 on a slide and cover with a few drops of methylene blue, allow it to 

 stain for several minutes, then wash away the excess of stain with 

 distilled water, add a drop of gum glycerine, tease, and mount. 



Study under high power, and search for olfactory and 

 sustentacular cells. Sketch a number of the cells as seen 

 under this power. 



