156 GEORGE E. NICHOLLS 
The filum terminale behind the lesion appears empty of fiber but 
an indistinct mass, which is apparently a tangled heap of fiber is seen 
in the sinus terminalis. In front of the lesion the fiber is slightly with- 
drawn, the end being swollen and somewhat spirally coiled. 
29. The incision was made at 4.20 p.m., August 7, and the ray was 
killed at 7.15 p.m. on August 10, no reaction having appeared in the 
meanwhile. Duration of experiment 3 days 3 hours. 
The sections establish that the incision failed to sever the filum 
terminale and the fiber which is unbroken maintains its normal diameter 
and is seen tautly stretched. 
41. The incision, made at 5.55 p.m., August 17, was followed, very 
quickly, by a reaction. The snout was lifted markedly and the whole 
body was arched up. The ray was disturbed several times but in- 
variably returned to rest in the same attitude. By 8.30 p.m. the 
reaction had become less pronounced and by noon next day, when 
the specimen was killed, it was much less marked. Duration of ex- 
periment 18 hours. 
In the terminal piece of the tail, Reissner’s fiber is found slack, 
swollen and retracted for some distance from the region of the experi- 
mental lesion. Another piece of the spinal cord, taken some consider- 
able distance in advance, showed the fiber very slightly slack and 
little swollen. 
49. The incision was made at 11.15 a.m., August 21. A marked 
reaction very quickly appeared, affecting the pose, both in swimming 
and at rest. At noon, the snout and tail were down but the body 
remained curiously humped up. The specimen maintained this atti- 
rude until it was killed at 1245 pm. Duration of experiment 14 
houcs. 
A conspicuous clot has formed in the region of the lesion and extends 
into the central canal both before and behind this point. Reissner’s 
fiber is seen extending backwards from this spot as a swollen, loose 
and slightly knotted thread. In front of the incision, the fiber emerges 
from the clot (fig. 22) markedly swollen and coiled interruptedly, in 
which condition it continues throughout the entire length of the piece 
of spinal cord examined. The penultimate piece reveals the fiber still 
more swollen and more markedly twisted. It is clear, therefore, that 
although there has been no withdrawal, in either direction from the 
region of the experimental incision, the fiber was, nevertheless, under- 
going a marked contraction. The only possible explanation was that 
the fiber had been broken farther forward and that a backward recoil 
had been set up, that having begun probably at or about the time of 
the operation. To test this point, another piece of spinal cord was 
taken from a place well forward in the trunk. The sections showed 
that, here, the central canal was perfectly devoid of fiber, a flimsy 
hollow cylinder of coagulum (?) occupying the center of the canal 
(fig. 18). 
51. The incision which was made at 11.30 a.m., August 21, was not 
apparently productive of any reaction. The specimen was killed at 
5 p.m. on the same day. Duration of experiment 53 hours. 
