MULLENIX: EIGHTH CRANIAL NERVE. 241 
structures described by Prentiss, Bethe, and others, are in reality 
nervous in character. It is not uncommon to find adherents of the 
neurone theory maintaining that the fibrillists have been misled by 
over-impregnation, and it is no less common to find adherents of the 
fibrillar theory attributing the conclusions of neuronists to the incom- 
plete impregnation of their material. 
It may well be recognized that the characteristics of nervous material 
by. which it may be differentiated from non-nervous material, in the 
study of neuro-histological problems, are not so numerous nor so 
varied as might be desired. A good deal of what we believe concern- 
ing the physiology of the sense cells and nerve fibres, particularly in 
the ear, rests upon analogical evidence which has not as yet been 
confirmed by experiment. It is probably safe to assume, however, 
that both the sense cells and the axis cylinders possess the physiological 
properties of nerve tissue, which Gotch, in his article in Schiffer’s 
Physiology (:00), has characterized as “‘that tissue which exhibits 
phenomena of excitability, conductivity, and states of excitation.” 
Without doubt these characteristics are possessed in common by sense 
cells and nerve fibres, though probably in varying degrees. Since it is 
as yet impossible to obtain direct evidence as to the functional differ- 
entiation between them, we are forced to-content ourselves with such 
morphological evidence as is afforded by differential staining, and to 
assume that those portions which exhibit peculiar affinity for silver 
compounds are nervous in character, as is undoubtedly the case in 
other places in the animal body, and that those which do not exhibit 
such affinity are non-nervous. Such a distinction is of course entirely 
inadequate as a general definition of nervous material, but it constitutes 
the best evidence that is obtainable at present, and it has seemed to 
me that it is well to recognize the narrowness of the tests upon which 
we are forced to rely in attempting to solve problems of this kind. 
My conclusion, then, regarding pericellular networks, is that the 
nervous character of such networks is doubtful, but that no violence 
would be done to the neurone theory by their confirmation. 
The theoretical significance of intracellular networks of neurofi- 
brillae, such as Kolmer has described, and of such intracellular struc- 
tures as Bielschowsky und Briihl have described, would depend to a 
large degree upon their embryological origin and the relations of the 
neurofibrillae of the sense cells to those of the axis cylinders. If it 
should be shown that the sense cells of the auditory epithelium are not 
secondary, but primary, sense cells, as is the case in the olfactory epi- 
thelium, it would seem that Apathy is right in ignoring the cell bodies 
