126 GEORGE E. NICHOLLS 
itself, were of little value, for it could not be established that 
any of the reactions observed were the results simply of the 
interruption of the ‘optic reflex short-circuit’ alleged to be pro- 
vided by Reissner’s fiber. 
I gather, moreover, that Sargent relied upon observations 
made from dissections to determine whether or not the experi- 
mental incision had really broken the fiber, which appears to me 
as an altogether unsatisfactory method. Whether there was a 
subsequent microscopical examination of the material is not 
clear nor does Sargent state what precautions were taken to 
prevent a disturbance of the fiber during the dissection. The 
statement that ‘“‘the cord and medulla of each individual was 
preserved for microscopical examination” suggests that a part 
only of the nervous system was subsequently cut out. If this 
were the case, it is practically certain that, whatever the result 
of the experiment upon the fiber, it. would be found retracted 
in the preserved material. 
It is, therefore, a little difficult to ascertain the grounds for 
his remark (’01, p. 450) that ‘“‘animals on which the equivalent 
operation was performed without breaking the fiber are nearly 
or quite normal.”’ 
Otber experiments were made by Sargent (’01) to determine 
the effect of artificial extirpation of the eye upon the fiber but 
the results obtained were never recorded. Several years later, 
experiments were made upon Reissner’s fiber by Horsley (08). 
In this case the subjects of the experiments were individuals of 
two species of Macacus. Minute electrolytic lesions were made 
in the spinal cord, at the level of the fifth cervical segment, in 
order to break the fiber. No observations are recorded, how- 
ever, upon the behavior of the living animals nor are details 
given as to the duration of the experiments. Concerning the 
appearance of the fiber under the microscope, Horsley remarked 
that Wallerian degeneration was not observed in the broken 
fiber. 
I find, however, some little difficulty in interpreting the ap- 
pearance of Reissner’s fiber in the sections figured by Horsley. 
