254 
DES. A. CAETE AND A. MACALISTEE ON THE 
the inferior, was marked below by a large smooth round aperture that led forwards and 
outwards to the inferior scala of the cochlea, the fenestra rotunda, above which was a 
sharp ridge that separated it from a large oval foramen, which was partly closed at its upper 
and anterior part by a thick scale of bone ; this aperture was directed into the jugular 
foramen behind, and into the highest part of the tympanic cavity in front. The external 
surface was deeply hollowed, and formed part of the superior and internal boundary of 
the cavity of the tympanum ; anteriorly it was marked by an opening for the transmis- 
sion of the corda tympani nerve which communicated with the aqueduct of Fallopius ; 
posterior and internal to this the fenestra ovalis was situated, which latter was closed 
accurately by the base of the stapes with its narrow end directed forwards, and its long 
axis pointing downwards and backwards ; it communicated with the vestibular cavity, a 
small space that presented on its superior, posterior, and internal part extremely dimi- 
nutive rudimentary semicircular canals. At the upper and outer part of the labyrinthic 
segment the aqueduct of the vestibule wound obliquely to the lower part of this cavity. 
The inferior posterior angle of the labyrinthic segment was prolonged backwards and 
almost touched the opisthotic portion, where it formed the inferior boundary of the 
large irregular foramen before noticed ; on the lower surface of this portion of the bone, 
the cochlea was exposed on removal of the superficial osseous substance, which was ex- 
tremely dense. 
The cochlea consisted of two turns, with the apex of the modiolus directed downwards 
and outwards ; the upper and inner part, or scala tympani, was somewhat larger than the 
lower and outer, the scala vestibuli. The lamina spiralis was deeply grooved for the 
reception of the filaments of the auditory nerve. 
The separate ossicles of the ear were but two in number, as the malleus was, correctly 
speaking, a process of the tympanic bone from which it projected upwards from the 
centre of its margin. It consisted of a short, stout handle, which was continued as a ridge 
of bone into the inner concave side of the tympanic cavity ; its upper or free portion pre- 
sented a rounded process (or capitulum) projecting outwards, surrounded by a slight 
groove that separated it from the articular surfaces for the incus; these latter surfaces 
were placed on the posterior aspect, and were twofold ; one larger surface, ovoid in shape, 
looked backwards, the second, directed upwards, was convex, and situated immediately 
below and at right angles to the former ; a minute canal traversed this bone, piercing it 
in a small triangular interval that separated the rounded extremity from the articular 
surfaces, and opened into the fossa beneath the rounded process above described. 
The incus in shape somewhat resembled one of the phalanges of a diminutive great 
toe ; it presented two concave articular facets on its posterior extremity, which corre- 
sponded perfectly with the surfaces on the malleus ; the distal end was rounded and 
bituberculate, but non-articular. On the upper surface a small oval facet was placed, 
covered with a discoid articular crust to articulate with the narrow extremity of the 
following ossicle, — 
The stapes, which was short, stout, and triangular in shape ; it consisted of two rami, 
