274 
DR. U. PRITCHARD ON THE COCHLEA 
epithelium is found ; this patch extends round the chamber, but is broader on its 
inner wall. 
This nerve epithelium is very similar to that of the maculae acusticae of the saccule 
and utricle'"'; thus it consists of a deep layer of small rounded cells connected with a 
superficial layer of ciliated ones—thorn cells and bristle cells. These are covered by a 
perforated cuticular membrane, through which the bristles and thorns pass ; the whole 
is surmounted by a loose mucoid mass, into which the thorns and bristles project, and 
which no doubt contain otoliths in the fresh stated 
The last bundles of the cochlear nerve pass forwards to supply this acoustic spot, 
and terminate in the nerve epithelium in the same manner as in the saccule and 
utricle of the vestibule. 
The course of the cochlear branch of the auditory nerve. —This passes through the 
substance of the bone a little to the outer side of the cochlea tube, and just above the 
level of the floor. As it proceeds forwards it gives off lateral bundles of fibres to the 
lamina ossea, its terminal bundles going to the lagena in the manner just described. 
Tracing these lateral bundles they soon enter and pass out of a ganglion, which 
consists of bi-polar nerve-cells, and is situated in the broad base of the osseous lamina 
at its commencement, but further and further inwards as it is traced forwards to its 
anterior end. The fibres from the ganglion collect again into bundles which divide 
and subdivide, uniting and reuniting so as to form a plexus; in this manner they 
pass through the lower portion of the lamina until the lower lip of the sulcus is 
reached. This is pierced with a single row of holes (habenula perforata), so that the 
nerve filaments may pass into the organ of Corti. At this point the fibres lose their 
myeloid sheaths, the axis cylinder alone entering the nerve epithelium. 
Comparison of interior of the cochlea of the Duckbill with that of the 
typical Mammal. 
As regards the scabe vestibuli and tympani the following differences are to be 
noted. In the ordinary Mammal there is not so much difference in size between the 
scala vestibuli and scala tympani, except at the base of the cochlea, where the latter is 
the larger. Again, the size of both seal® diminishes from base to apex of the cochlea 
in conformity with the general diminishing spiral. 
In the Duckbill the scala vestibuli is throughout larger than the scala tympani; 
and whereas the former diminishes its size, and alters its shape from the com¬ 
mencement to the end of the cochlea, the latter is throughout of the same size and 
shape. 
The Scala Media. —The scala media or ductus cochleae in the typical Mammal is a 
triangular tube, almost equilateral at its commencement at the base of the cochlea. 
* ‘ Quarterly Journal of Microscopical Science,’ p. 397, 1876. 
f In my specimens tlie acid decalcifying fluid lias dissolved out the otoliths. 
