228 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
In 1871 Retzius maintained that the epithelium of the maculae and 
cristae acusticae of fishes, amphibians, reptiles, birds, and mammals 
consists of only two kinds of cells,— the basal cells, which he identified 
with the “‘Fadenzellen”’ of Schultze, and the flask-shaped cells which 
bear the bristles. ‘The former he regarded as indifferent, or non- 
sensory, supporting cells, and the latter as the sense cells. He repre- 
sented the basal cells as bearing long threadlike processes which extend 
in one direction to the free surface of the epithelium and in the other 
direction to the basement membrane, the peripheral extensions occupy- 
ing spaces between the sense cells. 
Five years later Pritchard (’76) published an account of the histo- 
logical elements of the macula acustica of the sacculus in mammals 
(cat), in which he described a “cuticular membrane” bordering the 
distal ends of the sense cells and penetrated by the sense hairs. Be- 
tween the sense cells he represented triangular nucleated cells, with 
their bases intimately connected with the cuticular membrane and 
their apices prolonged downward, so that these triangular cells ap- 
peared to dovetail with the so-called “thorn cells,” which were doubt- 
less identical with what are commonly called the sense cells. 
This cuticula was designated by Kaiser in 1891 as a true limiting 
membrane, which he described as independent of the epithelial cells. 
In 1902 Held published a detailed description of the finer anatomy 
of the organ of Corti and other sensory structures of the mammalian 
labyrinth. He characterized the material found between the sense 
cells as supporting fibres which belong to the ‘‘ Fadenzellen”’ of Schultze, 
some of the fibres extending inward to the basement membrane, others 
extending outward to the region of the hair cells, where they are at- 
tached to the peculiar thickened network of cuticular substance which 
he described as investing the sense cells. 
Finally, in their recent paper Bielschowsky und Brithl (:07) have 
devoted considerable attention to the non-nervous elements of the 
auditory epithelium in mammals. They describe the epithelium as 
separated from the lumen of the ear by a limiting membrane, from 
which go off processes into the epithelium. ‘These processes have 
the form of isosceles triangles, the bases of which rest upon the limiting 
membrane, while the apices reach below the middle of the hair cells to 
the level of the nuclei of the ‘‘Fadenzellen.” Occasionally they found 
unstained fibres, which they regarded as belonging to the Fadenzellen. 
They believe these to be supporting structures, which are histo- 
chemically allied to cuticular substance. "They describe the ‘‘ Faden- 
zellen”’ as roundish structures with a dark, homogeneous protoplasmic 
oe 
