176 GEORGE E. NICHOLLS 
was pointed out that in the single example (8) in which the fiber, 
although broken, had failed to retract there had been no 
marked reaction. 
These conclusions, based upon the examination of material 
from a comparatively small number of experiments, are strongly 
supported by the results of the much more numerous experiments 
which were subsequently performed. The examination of the 
condition of Reissner’s fiber in several specimens which were 
not the subjects of experiment has provided further evidence in 
corroboration of the correctness of those conclusions. 
The results of this investigation may be said, therefore, to 
afford very definite confirmation of Dendy’s suggestion (put 
forward in 1909) that the fiber forms part of a mechanism 
which is concerned in the automatic regulation of the flexure 
of the body. ‘This hypothesis is quite in harmony, moreover, 
with certain observations recorded by Sargent (’04), although 
that author interpreted the facts in an altogether different sense 
(vide infra). 
I have been unable, however, to determine whether the re- 
action (the assumption of an unnatural attitude at rest and an 
abnormal action whilst in motion) is to be regarded as the con- 
sequence of the diminution of tension at the sub-commissural 
organ due to the slackening of the fiber or whether it is to be 
attributed to the putting out of action of a larger or smaller 
number of the scattered sensory cells EE in the epithelium 
of the central canal. 
It has been pointed out that, although there has been found, 
in some cases, a quite considerable retraction of the fiber in the 
hinder part of the spinal cord, accompanied by much swelling 
and spiral winding, yet in the anterior region of the spinal cord 
and in the brain itself the fiber may appear to be practically 
normal. In such a case it seems improbable that any appreci- 
able diminution in the tension of the fiber could have been felt 
in the region of the sub-commissural organ. Further, in those 
examples in which the slackness of the fiber has extended far 
forward, even though it be not accompanied by swelling, it is 
inconceivable that it could have taken place without rupturing a 
