ABSTRACT
The cartilaginous otic capsule is induced by the otocyst from surrounding mesenchyme, and this will later form the bony labyrinth, in which the membranous labyrinth is deeply embedded. Ford gave measurements of otic capsule length in the human fetus. Doden and Halves, from serial sections of human petrous bones examined by microradiography and circular polarized light, noted the following layers of bone, from inside (perilabyrinthine) outwards: an endosteal layer; endochondral; and inner periosteal. These three form the labyrinthine capsule proper. A series of annotated diagrams sums up the principal features of ear capsule growth in the rabbit. By computed tomography of the temporal bone in achondroplasia Cobb showed that changes derived from the overall hypoplasia of the petrous temporal bones affect the labyrinth within it. The situation of otosclerosis is most frequently in the region of the oval window (80-90% of cases), less frequently but often simultaneously (30–40% of cases) by the round window.
