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DR. U. PRITCHARD ON THE COCHLEA 
At the enlarged extremity (lagena) of the cochlea tube, which is entirely occupied 
by the membranous labyrinth, the lining is considerably modified, and a large patch of 
nerve epithelium is found, quite distinct in character and separate from the organ of 
Corti. This nerve epithelium is made up of cells exactly like those found in the 
macula acustica of the vestibule of Mammals* and Birds, i.e., with the alternating 
long bristles and thorns which project from the surface into a mucoid mass containing 
otoliths. The terminal branches of the cochlear nerve pass forwards to this patch of 
nerve epithelium, and terminate in the same manner as in the macula acustica of the 
vestibule. 
The interior of the cochlea of the Ornithorhynchus compared with that of the Bird. 
The differences between these two are so great that it will be well first to notice 
© 
the homologous and analogous parts in each, and then to consider the similarities and 
dissimilarities. 
In examining the drawings Nos. 2 and 8, it will be at once evident that the lamina 
ossea of the Ornithorhynchus (and other Mammals) corresponds to the quadrilateral 
cartilage of the Bird, and that the Mammalian ligamentum cochleae is represented in 
the Bird by the triangular cartilage. Also, that whereas the lower division or scala 
tympani of each corresponds, the ductus cochleae of the Bird occupies the whole of the 
upper division, and therefore corresponds to the scala vestibuli and scala media (or 
ductus cochleae) of the Mammal. On more minute examination, the peculiar folded 
tegmentum of the Bird will be found to take the place of the stria vascularis and 
membrane of Reissner of the Mammal; and by carrying the examination into the 
foetal condition, the peculiar hyaline columnar cells of the quadrilateral cartilage will 
be found homologous with the teeth of the Mammalian limbus, which is represented 
in the early foetus by very similar cells. 
Dissimilarities in the Bird's cochlea :— 
The absence of the scala vestibuli and membrane of Reissner. 
The gradual tapering and final termination in a cul-de-sac of the scala tympani. 
The cartilaginous condition of the structure corresponding to the Mammalian 
ligament. 
The cartilaginous condition of the structure which corresponds to the lamina ossea. 
The cartilaginous tubular formation towards the apex of the cochlea. 
The tegmentum, with its folds and peculiar pigmento-granular cells. 
The absence of the marginal sulcus. 
The absence of the rods of Corti. 
The large number of rows of hair cells. 
The matting together of the hairs into a sort of spine. 
The numerous perforations for the passage of nerve filaments into the organ of 
Corti. 
* ‘ Quarterly Journal of Microscopical Society,’ October, 1876. 
