18 
GEORGE E. NICHOLES. 
animal, but states that, although he was able to follow it 
forwards into the cavity of the mid-brain, he could determine 
neither its origin nor its ending. He disagrees with Sargent 
as to its nervous nature, and inclinesrather towards Studnicka’s 
view of its origin and character. In his summary he states 
(p. 209) : “ Der Centralkanal enthiilt konstant den Achsenfaden 
(Reissner’sclie Fadeu). Es ist siclier kein nervosen Gebilde, 
walirscheiulich ein Sekretionsprodukt der Ependymzellen.” 
In the same year Sargent’s theory was accorded a place in 
vol. ii of Sedgwick’s ‘ Text-Book of Zoology’ (’05), where it 
is stated (p. 195) that Reissner’s fibre “consists of a bundle 
of nerve-fibres and communicates with the tissue of the spinal 
cord throughout its length. It appears to be absent in blind 
fishes.” 
Uendy, in 1907, described and figured the fibre in Geotria 
australis, calling attention to its relation to the sub-com- 
missural organ (ependymal groove). He suggested a possible 
connection with the pineal eye, a vieAv which he has since 
abandoned, and, while accepting Sargent’s theory as to the 
nature and function of the fibre, said (p. 15): “I find it 
difficult to believe that such a remarkable and well-developed 
structure as the ependymal groove should be required solely^ 
for the function which Sargent assigns to it.” 
In the same year (1907) Sargent’s work obtained notice in 
several text-books. Johnston (’07, p. 148) put forward the 
optic reflex theory with a certain I’eserve, but, so far as I can 
find, his work contains no reference to the sub-commissural 
organ ! Sherrington (’07) apparently accepted the optic 
reflex theory freely, and in the English edition of 
Weidersheim’s text- book (’07) it also finds a place, 
though only in a footnote. 
In 1908 I announced in ‘Nature’ (’08) the presence of 
Reissner’s fibre in the frog, and called attention to its 
relation to the snb-conunissural organ in that animal.' 
' I have since found that the fibre had previously been seen in the 
canalis centralis of Rana by Stieda ('70), although he did not 
refer to it by name, and considered it to be an artifact. 
