NERVE TERMINATIONS OF THE TADPOLE. 67 
I am, therefore, inclined to believe that Mitrophanow 
drew his conclusions from a study of preparations not sufli- 
ciently successful. In no other way can I account for his 
confusing two kinds of terminal nerve-fibrils and for his over- 
looking the sub-epithelial network. If this explanation is 
correct, then it will be easy to understand why he observed no 
intracellular nerve terminations. 
It seems remarkable that the intra-epithelial nerve-fibrils 
should take their origin, some from the fundamental plexus, 
some from the sub-epithelial network. There must be some 
physiological significance in this arrangement. Pfitzner believes 
that each of the two fibrils described by him as terminating 
within every epithelial cell represents a channel for a special 
kind of nervous impulses, one fibril corresponding to a path 
for motor, the other to a path for secretory impulses. The 
intracellular fibrils, as I have found them, arise from the sub- 
epithelial network, and the number distributed to each cell is 
not limited to two, but is very often more. Consequently, 
one can hardly imagine that they have different functions to 
perform. On the other hand, the different modes of origin 
of all intra-epithelial fibrils, as described above, might well be 
supposed to correspond to some differences in function. In 
that case the fibrils from the fundamental plexus terminating 
directly between the epithelial cells might serve as paths for 
sensory impulses, while the sub-epithelial network with the 
intracellular and intercellular fibrils arising from it might 
conduct secretory or trophic impulses. 
I am unable to suggest any reason for the occurrence of 
more than one termination within every cell. 
The question may be asked, why the intracellular fibrils of 
the basal and intermediate layers of the epithelium possess 
sheaths in the form of figures of Eberth, while those of the 
majority of the superficial cells have no such sheaths? Also, 
why are the figures of Eberth completely absent from the skin 
of the adult frog? These questions are difficult ones to 
answer, but I may suggest several data which will, probably, 
assist in their solution. The cells of the intermediate and 
