THE FINE-STRUCTURE OF THE GUINEA-PIG TYMPANIC MEMBRANE WITH SPECIAL REFERENCE TO THE FIBER ARRANGEMENT

The tympanic membrane of the guinea pig was studied by electron microscopy. The pars tensa was composed of three layers, i.e., the outer epidermis, the middle lamina propria and the inner mucosal membrane. The pars flaccida was negligible in size. The fibers in the lamina propria of the tympanic membrane were not clearly observable by conventional electron microscopy. With the silver methenamine method the fibers were more intensely stained than the epithelial cells and could thus be distinctly demonstrated by this method. In the inferior larger portion of the pars tensa, the lamina propria contained the outer radial and the inner circular fiber bundles. The radial fiber bundles were thicker and more densely packed than the circular ones. This fact indicates that the radial fibers form the major skeleton of this portion. The superior smaller portion of the pars tensa contained several layers of irregularly arranged fiber bundles in the lamina propria and was considerably thicker than the inferior larger portion.