THE FUNCTION OF REISSNER’S FIBER 137 
Subsequent examination of this material under the microscope 
indicated that in most cases it would be necessary to examine 
only an inch or so of the spinal cord in front of the place where 
the incision was made. This point was almost always within 
a third of an inch of the extremity of the tail. The size of the 
specimen thus appeared to be of no great importance but this 
fact was only ascertained when the material had been prepared 
for microscopic examination nearly a year subsequently to the 
completion of these preliminary experiments. 
Accordingly in the summer (August) of 1911 I was less care- 
ful to restrict my experiments to specimens of small size. I was 
thus enabled to obtain, more readily, the many specimens which 
I required. In all, a dozen comparatively small dogfish, ranging 
from 14 to 20 inches in length, were secured, and, upon these 
were performed experiments varying in duration from a few 
(three) hours in some cases to more than eighteen days in others. 
_ Of the rays, three species were employed, but of one of these, 
Raia microcellata, I had but a single specimen and, as in the 
previous year, the greater number of the experiments were made 
upon specimens of R. clavata and R. blanda. These included 
rays which were barely 6 inches in length and which were, pre- 
sumably, just escaped from the egg case, while others ranged up 
to 16 inches. The duration of the experiments, in the case of 
the rays varied from a few (ten) minutes to as much as thirteen 
days. 
The actual operation consisted in severing Reissner’s fiber 
at a point quite near to the hinder end of the terminal filament 
and was practically nothing but a simple prick which rarely 
drew a drop of blood although, in some cases, the sections showed 
that there had been some effusion of blood into the canalis 
centralis. 
Notwithstanding its trivial character, however, I was obliged 
by the conditions under which the vivisection license was issued, 
to perform the operation only upon anaesthetized specimens. 
Some trial experiments with the anaesthetic indicated that 
dogfish were curiously susceptible to chloroform and, despite 
