THE FUNCTION OF REISSNER’S FIBER 159 
16. The incision was made at 12.15 p.m. When the ray was re- 
turned to its tank, the tail was seen to float slightly off the floor but 
with the visible return to consciousness, the ray took up the normal 
position. The specimen appeared very inert and, upon examination 
made next day, it was found that the vertebral column had been com- 
pletely broken at a point some distance from the end of the tail. The 
specimen was killed at 10.30 a.m., August 23, some 22 hours after the 
operation. 
Sections through the end of the tail showed that the hinder end of 
the spinal cord had already largely degenerated, obviously as the re- 
sult of the accident which had broken the tail. 
17. The incision which was made at 2.30 p.m., August 2, was fol- 
lowed very quickly by a curving up, lengthwise, of the body and 
snout. This reaction persisted throughout the remainder of the day. 
Next morning the specimen was found in the normal attitude. It was 
killed at noon. Duration of experiment 215 hours. 
The sections show that the fiber had withdrawn wholly from the 
terminal piece. The penultimate piece of the tail was subsequently 
sectioned but the fiber was absent from the length of spinal cord in- 
cluded in these sections, also. 
18. The incision was made at 2.40 p.m., August 2, but no reaction 
was apparent. The specimen was kept under observation until noon, 
August 9, when it was killed. Duration of experiment nearly 7 days. 
The sections showed that the fiber was broken by the operation 
and has, in the small severed portion of the terminal filament, entirely 
disappeared, while this piece of the terminal filament itself appears 
to have largely degenerated. In front of the lesion, the fiber stretches 
backwards practically to the point where it had been cut. Near its 
free end it is, however, slightly swollen and a little slack and its actual 
extremity is distinctly fibrillated (fig. 28), the flaring of the extremity 
suggesting that a terminal plug was in process of formation. There 
was, when the specimen was killed, no new terminal sinus formed. A 
little in front of the actual end the fiber is little swollen and runs 
nearly truly in the center of the canal, surrounded by an extensive 
blood clot which doubtless prevented the retraction of the fiber. 
26. The incision was made at 4 p.m., August 7, but no reaction ap- 
peared during this or the three following days. The specimen was 
killed on August 10, at 6.30 p.m. Duration of experiment 3 days 25 
hours. 
Reissner’s fiber is seen in the sections as an extremely fine thread 
stretching forward tautly from the point of experimental incision and 
there has, apparently, been no retraction. 
28. The incision was made at 4.20 p.m., August 7,and produced no 
apparent reaction. The ray was killed on August 10, at 6.15 p.m. 
Duration of the experiment 3 days 2 hours. 
The fiber has evidently not retracted, in either direction from the 
point of incision being held, apparently, by the adpressed walls of the 
terminal filament. 
