COCHLEA. SEMI-CIRCULAR CANALS. 105 



the lower turn punctured, (p. 9 for one hour, transfer to half 

 strength 14a until decalcified, then increasing alcohols, s. 22 

 and 24, c. C, clear in origanum oil, m. B.) (L) Find the coch- 

 lear tube in section and the osseous spiral lamina which 

 projects into it. The latter has two lips separated by the 

 sulcus spiralis. From the longer (tympanic) lip, the basilar 

 membrane stretches across the tube to be attached to its 

 outer side by the spiral ligament. Inwards from the upper 

 (vestibular) lip or limbus the membrane of Reissner, one cell 

 thick, stretches to the outer wall, where it becomes continuous 

 with the epithelium of the spiral ligament, thus enclosing the 

 triangular cochlear canal of the membranous labyrinth. That 

 portion of the cochlear tube which lies outside the basilar 

 membrane is the scala tympani (to fenestra rotunda), and 

 that outside Reissner's membrane is the scala vestibuli (to 

 fenestra ovalis). The lamina spiralis ossea contains the spiral 

 ganglion and nerves passing to the organ of Corti. The mem- 

 brana tectoria attached to the surface of the limbus is fusiform 

 in section, with its free end curled up, and extends over 

 Corti's organ. (//) The organ of Corti, with its inner and 

 outer (rods) sustentacular cells (enclosing the spiral canal), 

 reticular membrane, hair and Deiter's cells, then Hensen's cells 

 on the external side forming a rounded mass, become contin- 

 uous with the flatter epithelium lining the remainder of the 

 canal. The stria vascularis, a thickening . of the membranous 

 wall, is placed between the spiral ligament and the attachment 

 of Reissner's membrane. In this preparation a section of the 

 Eustachian tube is often included. It consists of an incomplete 

 tube of hyaline cartilage, lined by a thin mucosa, with a 

 superficial covering of columnar ciliated epithelium. 



Semi-circular Canals. L.S. Ampulla, Guinea pig. (p. osmic 

 1 1KC - 4 hours, then 14 (a), s. 22 & 24, c. P., m. B.). (L & 11} 



