166 GEORGE E. NICHOLLS 
VI. THE RELATION BETWEEN THE CONDITION OF REISSNER’S 
FIBER AND THE REACTION OBSERVED 
1. In the subjects of the experiments 
1. Of the six specimens included in the first group two were 
dogfish. The duration of the experiment varied from a little 
less than 6 hours (51) to nearly 19 days (23). In not one of 
these specimens, in which the experimental incision failed to 
break the fiber was there any reaction. 
2. In the second class come nine specimens in which, although 
the experimental incision was successful in breaking the fiber, 
this did not undergo retraction forward from the lesion. All 
but one of these specimens were rays and the duration of the 
experiment varied from three-quarters of an hour (38) to nearly 
7 days (18). For the most part, however, the specimens were 
killed in the first or second day. 
Six specimens were not visibly affected by the operation, 
while the remaining three exhibited a scarcely perceptible re- 
action. This took the form either of a very slight uplifting of 
the tail for a quite brief period (8) or of a trifling elevation of the 
snout (36, 42). 
It would appear, therefore, that a mere breaking of the fiber 
which is, for any reason, not followed by retraction is unlikely 
to evoke a reaction and, presumably, does not disorganize the 
mechanism of which Reissner’s fiber forms part. 
3. A comparison, however, of the records of the experiments 
with the evidence afforded by the microscopical examination of 
the preserved material in the case of the thirty individuals 
composing the third group, suggests that there exists a distinct 
connection between the reaction manifested and the retraction 
of the fiber. 
Thus in certain cases (e.g., 37, 52, 53, 64, 66) in which the 
reaction had not been particularly pronounced or prolonged, 
there was found to have occurred a comparatively slight retrac- 
tion. On the other hand, in a number of experiments (10, 20, 
22, 24, 35, 438, 54, 56, 57, 58, 59, 60, 67, 68) in which the reac- 
tion had been particularly marked there was found to have 
