416 
of the fibre, I was naturally desirous of securing moderately small 
specimens for it must be remembered that there was a possibility that 
the entire length of the central nervous system of all of the specimens 
might have to be examined in serial sections. 
Comparatively small skates (Raja blanda and R. clavata) from 
eight inches in length upwards were, however, available, and the larger 
number of experiments were, in consequence, performed upon these. 
In the result, it proved to be necessary to examine only an inch 
or so of the spinal cord in front of the point where the incision was 
made, which was rarely more than a quarter of an inch from the 
very tip of the tail. Thus the size of the specimens was not really 
material, but this knowledge was only gained when the sections were 
cut, some time after the experiments had all been performed. 
The operation was a very slight one, consisting simply in severing 
Reıssner’s fibre by a single thrust of a fine knife blade through the 
hinder end of the terminal filament near its extremity. It was, indeed, 
little more than a simple prick which rarely even drew a drop of 
blood, although examination of the sections showed that there had 
been, in some cases, a slight internal haemorrhage. 
Since, however, the conditions attaching to the licence under which 
the experiments were permitted, required that the operation, notwith- 
standing its trivial character, should be carried out upon anesthetized 
specimens, some trial experiments were made to determine the degree 
of insensibility which might safely be induced. 
A small quantity of chloroform!) was thoroughly shaken up with 
a relatively large volume of sea water and a little of the mixture 
added to the water in the vessel which contained the fish. It was 
found that a quite short stay in this dilute chloroform water proved 
fatal, for the animal though continuing to live for some time did not 
recover consciousness. 
Finally it was found that only a very brief stay in the chloroform 
water was all that could be allowed, the anzsthetic proving a much 
more serious matter to the animal than the operation itself. 
Notwithstanding the experience gained in this preliminary experi- 
mentation I had, subsequently, two of my experiments (out of a total 
of eleven) nullified by the failure of the specimens to recover from 
the effects of the anesthetic. 
The operation was quite easily carried out, the specimen being 
removed from the water and placed upon the table with the tail 
1) In a few later cases, the quantity of the chloroform was re- 
duced and a little ether added. 
