THE FUNCTION OF REISSNER’S FIBER 153 
B. Raia blanda 
3. This specimen was one which failed to recover from the anaes- 
thetic. Some 2 to 3 hours after the operation it appeared to be dead, 
the central nervous system, therefore, was partially exposed and 
preserved. 
The sections show that the incision severed the fiber but at the 
same time apparently pinched together the walls of the terminal fila- 
ment sufficiently to hold the cut ends. Behind the incision, therefore, 
the fiber is found, stretching backward from the region of the lesion 
to the sinus terminalis. It is somewhat swollen, the swelling becom- 
ing more marked as the terminal sinus is neared and, actually within 
the terminal chamber, it becomes greatly swollen and coiled. The 
terminal plug is obscured by this retraction and cannot be certainly 
identified (text-fig. 4). 
In front of the lesion Reissner’s fiber is found, everywhere in the 
length of the terminal filament examined, much swollen and most 
remarkably coiled, all the later stages of spiral winding (short of the 
production of actual tangles) being found in this short extent of cen- 
tral canal (text-fig. 2). Regions in which the fiber is simply twisted 
alternate with others in which the coiling is quite complicated and it 
is probable that the original (uncontracted) length of the fiber included 
in the piece examined was many times that of the length (about # 
inch) of the containing central canal. The evidence suggests, there- 
fore, that there must have been in progress, at the time the incision 
was made, a very definite retraction of the fiber in a backward direc- 
tion from a point well in advance of the experimental cut. This cut 
clearly checked further retraction behind the lesion, but in front the 
retraction probably continued until it was stopped by the hardening 
action of the fixing fluid several hours subsequent to the operation. 
4. The incision was made at 10 a.m., July 8, and was followed by a 
quick recovery. Thereafter, the fish swam about with its tail turned 
dorsally. Six hours later, when seen at rest, it was noted that its tail 
was turned sharply to one side and that the extremity was raised at 
least an inch. The tail was still lifted at 9.30 a.m. next day but later 
this peculiarity was less pronounced. The specimen was killed at 3 
p.m. Duration of experiment 1 day 5 hours. 
The sections are poor and very obliquely cut. A considerable clot 
occupies the central canal for some distance in either direction from 
the experimental lesion. Behind the region of the incision I have 
failed to recognize Reissner’s fiber but in front it can be made out 
vaguely, apparently lying somewhat slackly against the epithelial 
lining of the central canal and with some trace of irregular swelling 
and coiling (fig. 16). 
7. The incision was made at 10.30 a.m., July 9, and was quickly 
followed by an elevation of the end of the tail, the whole tail being 
turned slightly to one side (the left). By July 11 the fish appeared to 
have become normal, excepting that it continued to exhibit a prefer- 
