Scanning E. M. observations of the middle ear mucosa were scrutinized two weeks after transtympanic infusion of several fluids with different osmotic pressure. Whirl pool like arrangement of cilia was detected from the epitympanic area of the normal middle ear mucosa. Shortening or molt of cilia were demonstrated by the low osmotic pressure fluids. Also hyperfunction of secretory cells were detected. The cases of high osmotic pressure fluids demonstrated not only above, but also the increase of microvilli on the non-ciliated cells. The damage of the ciliary movement and the impediment of the mucosal clearance were demonstrated by the fluids of high osmotic pressure.
