PLATE 4 
EXPLANATION OF FIGURES 
24 Raia clavata (5). A transverse section (shghtly obliquely cut) through 
the filum terminale, at a point a little in front of the sinus terminalis. Several 
fibrillae are seen which have apparently broken free from the displaced and 
slack Reissner’s fiber. X 320. 
25 Raia clavata (XIX, not experimental). Part of a sagittal section through 
the filum terminale. Posteriorly the fiber is seen swollen but fairly regular. 
It passes into a tightly tangled knot, from the anterior end of which it emerges, 
loosely coiled. (Posterior end to the left, in the figure.) > 240. 
26 Raia blanda (10). Part of a sagittal section of the hinder end of the 
spinal cord, some half inch in front of the lesion. The posterior end of an ex- 
tensive but loosely tangled skein of Reissner’s fiber (of nearly normal diameter) 
is seen in the central canal which is cut obliquely. (Posterior end to the left 
in the figure.) X 320. 
27 Raia clavata (64). Part of a sagittal Section through the filum ter- 
minale in front of the lesion. Reissner’s fiber is very fine and, to the left (ante- 
rior) of the figure is seen in apparent contact with the wall of the central canal. 
Behind this point it lies slackly, well away from the wall of the canal. X 320. 
28 Raia clavata (18). Part of a sagittal section through the filum ter- 
minale, immediately in front of the lesion. Retraction of the fiber was pre- 
vented by the formation of an extensive clot (lying more anteriorly and not 
shown in the-figure). The severed end of the fiber is seen fibrillated and flaring 
as though to produce a new terminal plug. X 240. 
29. Salamandra maculosa. Part of a transverse section through the spinal 
cord. Reissner’s fiber apparently receiving three or four constituent fibrillae. 
Near the dorsal line there projects a conical process which is probably the apex 
of a sensory cell. X 340. 
30 Seyllium canicula (44). Part of a sagittal section through the filum 
terminale showing the unretracted fiber, with what are apparently constituent 
fibrillae in situ. > 340. 
31 Seyllium ecanicula (2). Part of a sagittal section through the filum ter- 
minale at the point where this was severed by the experimental incision. The 
cut end has become rounded off and the meninges have grown around it to com- 
pletely enclose the secondary sinus terminalis. The end of Reissner’s fiber is 
seen flaring somewhat and has, apparently, made good its new attachment. 
x 340. 
ABBREVIATIONS 
c.c., central canal of the spinal cord mn., meninges, forming the hinder 
(and terminal filament) wall of the sinus terminalis’ 
d.b.v., dorsal blood vessel R.f., Reissner’s fiber 
e., epithelium lining the central canal s.p., sensory process (?) 
fb., fibrillae of Reissner’s fiber in the s s.l., secondary sinus terminalis 
central canal ** indicate the region of the incision 
{.t., filam terminale 
LYS 
