THE FUNCTION OF REISSNER’S FIBER 169 
animal, the experiment would have been found to belong to the 
third of my four classes. 
The case of no. 19 is of a different kind. In this specimen 
no reaction appeared as the result of the operation yet, in the 
sections, the severed end of the fiber in front of the lesion was 
found to be retracted for a short distance, swollen and, near its 
free end, spirally coiled. The latter detail probably affords the 
clue to what might, in view of the absence of any reaction, ap- 
pear as a distinct anomaly. The experiment had continued for 
6 days and, therefore, if there had taken place a retraction of the 
fiber so extensive that the fiber had not straightened out in that 
time, a well marked reaction should have been evident. Spiral 
coiling, however, in every other instance known to me, is asso- 
ciated, as I shall show, with recent retraction. In this in- 
stance, then, there can be little doubt, I think, that the specimen 
was one which would in the ordinary way have been included in 
the second group—i.e., among those in which the fiber was sev- 
ered but failed to retract—the severed end being gripped, prob- 
ably, by the compression of the walls of the filum terminale. 
During the handling which is unavoidable where a rapid dis- 
section is desired, the fiber may have been released and then have 
commenced to withdraw. <A disturbance which freed the fiber 
from the grip of the walls of the filum terminale doubtless af- 
forded, at the same time, ready ingress to the fixing fluid and 
thus quickly checked the incipient retraction. 
In the last experiment performed (70) there was again an ap- 
parent discrepancy. This specimen on recovering from the 
anaesthetic, assumed a quite unusual position (fig. 10) which 
appeared to be an obvious reaction to the experiment. Subse- 
quent examination of the material under the microscope re- 
vealed, however, that the experimental incision had just failed 
to cut the filum terminale. As it happens, the greater part of 
the filum terminale in the piece of tissue sectioned is contained 
in one thick section in which, although the presence of Reiss- 
ner’s fiber can be ascertained, it is not possible to make out its 
condition. Owing to a slight distortion of the material, however, 
the sinus terminalis lies in an adjacent section which is moder- 
