No. 1.] EPITHELIUM OF MUSTELUS CANIS. 63 
found to exhibit many varicosities in their course which vary 
greatly in size. The largest varicosities were nearly as large 
as the ganglion cells. It was thought, from results still unpub- 
lished obtained with Ehrlich’s method, that these varicosities 
were of a cellular nature, probably sheath cells. The nerve 
fibers stained in this way were found to be uniform in size. 
Dr. Ayers considers the hair cell as a genuine nerve cell and 
the cell of origin of the auditory nerve fiber. He thinks that 
at an early stage of development the ganglion cells are produced 
by the division of the superficial hair cells, and as development 
advances a protoplasmic thread connects the two cells. The 
nerve fiber soon begins to develop from the proximal end of the 
bipolar ganglion cell and extends to the brain. The relations 
existing between the hair cells and nerve fibers in the maculae 
and cristae acusticae were found to be essentially the same as 
in the cochlea only simpler. In the summary we find these 
statements: 
“That there is no fundamental difference between the 
acoustic and olfactory elements yet made known.” 
“ That all fibers of the auditory nerve proceed out of hair 
cells alone so far as has yet been satisfactorily determined.”’ 
Niemack ('92), in his observations on the auditory epithelium 
of the frog and rabbit with Ehrlich’s method, found that the 
nerve after losing its sheath divided dichotomously many times. 
The final branches were of equal size, and, after rising to the 
level of the proximal ends of the hair cells, extended horizon- 
tally, forming a close network about their bases or a kind of 
sieve, in the meshes of which the hair cells rest. He found, as 
Kuhn had previously done in fish and amphibia, two kinds of 
nerve endings: one connected with the proximal ends of the 
hair cells, while in the other the nerve fibers pass in the inter- 
stices between the hair cells to end free at the surface in knob- 
like enlargements. Niemack found triangular swellings in the 
nerve fibers at their point of branching, as had been previously 
observed by Retzius. In the maculae he found a granular layer 
separating the nerve fibers from the base of the hair cells; a 
thin mantle of violet granules was also found covering the 
surface of these cells. 
