, 
580 The Sensory Organs. | September, 
_ It will be found most expedient to commence with the organ 
of hearing. 
Here the percipient structure is either situated in, or consti- 
tuted by, the epithelium of the maculz acustice of the ampulle 
and saccules, and by Corti’s organ. Concerning //7s there can be 
no doubt, and were we to analyze the subject no farther, it would 
be sufficient for our purpose. The epithelium of the macule 
acusticæ, as we know, is made up of several kinds of cells. 
Prominent among these is one bearing a hair-like structure on its 
peripheral end, and possessed of central out-runners or processes. 
Now regarding the distribution of nerve-fibres to these acoustic 
spots we may hold the following views: either that the nerves 
end in plexuses and loops zz or immediately dencath the epithel- 
ium, or that they are directly continuous with either the cylin- 
drical, the stellate or the hair-bearing cells. Almost any one of 
these suppositions would suffice for the main points of the gen- 
eralization I have in mind, but when we turn to the literature 
bearing immediately on this point, we learn that the constant or 
essential element of the macule acustice, and in fact of the 
organ of hearing, appears to be a cell bearing a central and a 
peripheral process. This cell is constant throughout vertebrates 
and, as far as known, throughout invertebrates. The entire liter- 
ature makes it also more than probable that these cells are 
directly continuous with nerves. Thus, Max Schultze already in 
1858 (Muller’s Archiv), in speaking of the ultimate nerve ter- 
mination in the ear of the petromyzon, ray, pike, etc., advanced 
strong grounds in support of this view. Deiters, in 1860 (M.A.), 
described the hair-cells of birds, and considered their connection 
with nerves probable, while in 1862 U) he described the hair- 
cells of amphibians, and in the “lagena” believed them to be 
directly continuous with nerves. About this time, also, F. E. 
= Schulze claimed to have seen the direct transition of nerve fibres 
into the auditory hairs of young sea gudgeons. In 1867, Hasse 
(Zeitsch. d. Wissensch. Zoölogie, Bd. xvii) described the hair-cells 
of birds, and said that he clearly made out the entrance of the 
=~ nerve-fibres into them. He said that he frequently traced the 
~ central processes of the cells for long distances in the course of 
_ the nerveé-fibres, and vice versa, he traced the nerve-fibres in the | 
. direction of the central processes. Odenius, 1867 (A. f. M. A), 
Ivocates or man the same Me He says, that all cnapan 
