ss. 
it seems that snarls formed by such backward recoil into the terminal 
sinus may be more or less enduring, it would appear that a tangle 
formed by recoil forward (unless it be very extensive) straightens out 
again quite quickly and the fibre grows backwards to make a fresh 
attachment. This seems to indicate that growth takes place only 
from in front, backwards. In ordinary accidental breakage the new 
attachment appears to be directly into the wall of the sinus terminalis 
immediately adjacent to the tangled mass of fibre which had settled 
down upon the earlier attachment, so that it often appears to emerge 
from the tangle itself. In the case of the dogfish (2) a secondary 
sinus terminalis was formed in front of the lesion. If the process of 
regeneration had been permitted to continue it is probable that the 
portion of the filum terminale which lay distal to the lesion would 
have ultimately degenerated and disappeared. In that event, the 
filum terminale would naturally have grown backwards to replace 
it. In such circumstances the normal tension of the fibre might 
readily be reéstablished by growth, and that same phenomenon would 
probably account for restoration of the normal tension in cases of 
accidental breakage of the fibre in growing animals, but by what 
means the tense condition of the fibre would be restored naturally in 
a case of its accidental breakage in a full grown animal, I am unable 
to suggest. 
I desire here to express my thanks to Mr. R. W. H. Row for 
making many of the photomicrographs used in illustration and to Mr. 
C. BıppoLpH for assistance with the section cutting. 
Sept. 2nd, 1911. 
Literature referred to. 
1909 Denpy, The Function of Rerssnur’s Fibre and the Ependymal 
Groove. Nature, Vol. 82, p. 217%. 
1910 Denpy and Nıcnorzs, On the Occurrence of a Mesocelic Recess 
in the Human Brain, and its Relation to the Sub-Commissural 
Organ of Lower Vertebrates; with special reference to the 
Distribution of Reıssner’s Fibre in the Vertebrate Series and 
its possible Function. Proc. Roy. Soc., Vol. 82. 
1908 Epınger, Vorlesungen über den Bau der nervösen Zentralorgane 
des Menschen und der Tiere, Bd. 2, Leipzig 1908. 
1908 HorsLey, Note on the Existence of Reıssner’s Fibre in Higher 
Vertebrates. Brain, Vol. 31. 
1908 NıcHoLıs, Reıssner’s Fibre in the Frog. Nature, Vol. 77, p. 344. 
1909 —, The Function of Reıssner’s Fibre and the Ependymal Groove. 
Ibid., Vol. 82, p. 217—218. 
