No. I.] THE VERTEBRATE EAR. hq 



while the Hensen-Helmholtz theory introduces strange processes 

 unknown elsewhere in animal physiology. 



Retzius and most of the authors who had dealt with this 

 topic before his time have maintained that the auditory hairs 

 of the cochlear cells were not only short thick rods and quite 

 stiff, but were inserted into the cell cap in a more or less cres- 

 centic line. Waldeyer and Gottstein, while agreeing with Ret- 

 zius as to the length of the auditory rods or bacilli, do not 

 agree with him as to the manner of insertion, claiming that the 

 rods are certainly distributed over the entire surface of the 

 cell end, and that with a nearly even spacing. They consider 

 these rods to be distinct each for itself. When, however, we 

 come to the auditory hairs of the other parts of the ear, all 

 authors who mention the structure of the basal portion of the 

 hairs describe a striated appearance due to fibrillce, as Hensen 

 claimed, and in this he was corroborated by Retzius. 



These hair fibrillae were found to number 18-20 per cell on 

 cells of the ampullar sense organs of fishes, and a single fibrilla 

 measured at its base 0.7/1, in diameter ; they were the constituent 

 elements, as Retzius agreed, of round hairs. Their terminal 

 ends were not described by these authors. Retzius has figured 

 the hair cells (and several other authors have done the same, 

 notably Hasse, Paul Meyer, and Hensen) from all sense organs 

 of the ear other than the cochlear organ, as surmounted by 

 a bundle of more or less broken fibrillae, which he explains 

 are the ultimate fibrillae of the auditory hairs, but in every case 

 attributes their individuality to the effect of reagents or mechan- 

 ical injury. In Proteus the fibrillae, or, at least, the striations 

 indicative of their existence, were traced to near the tips of the 

 auditory hairs. I think there can be no doubt as to the accu- 

 racy of these observations so far as they go, but the question 

 arises, Do these fibrillae remain compacted into bundles as is the 

 case with the auditory hairs of the majority of the auditory 

 sense organs, or are they separated during life .'' In the case of 

 the organ of Corti, where the auditory cells are much more 

 closely set than in the other sense organs, the fibrillae or ulti- 

 mate hairs certainly are independent of each other to a degree 

 not found in preparations of the other sense hairs. Compare 

 the cochlear hair cell from the opossum (PI. VIII, Fig. 9) with 

 the hair cells from the mocking-bird's ear (PL VI, Fig. 9). 



