and the formation of artifacts in the lumen of the same. Among those 
used were: FLEMMING’s stronger fluid, formol, corrosive-acetic, ZENKER’S 
fluid, potassic bichromate, bichromate-formol, picric-formol-acetic, GIL- 
son’s fluid, MÜLLER’s fluid, Grar’s chrome-oxalic fluid and chromic acid. 
In material preserved in any of the fluids enumerated the fibre can be 
plainly seen, being, however, somewhat more sharply brought out by 
some than others. 
The stains which serve best for the study of Reissner’s fibre are 
certain hematoxylins and certain anilines. Of the first class MALLORY’s 
phosphomolybdic and phosphotungstic hematoxylins, and EHRLICH’s 
acetic-alum hematoxalin were the best. Iron hematoxylin brings out 
the fibre well, if decolorization is not carried too far. Of the anilines 
methylen blue, Congo red and acid fuchsin were found most valuable. 
Double staining was found desirable to bring out the internal structure 
of the fibre. The most successful combination was EHRLICH’s hemato- 
xylin followed by Congo red, which, by the way, is far the best of 
all combination stains for the central nervous system of lower Verte- 
brates. GoneGi methods have so far failed to give an impregnation of 
REISSNER’S fibre. 
In Teleosts the canalis centralis is lined by conical or columnar 
epithelial and ependymal cells throughout its length. The epithelial 
cells are ciliated, the cilia in a larval Amia 15 mm long, are 5 w in 
length, equaling one forth the diameter of the lumen of the canal. 
Within the lumen of the canalis centralis and in the brain ventricles 
one finds 1) a coagulated and shrunken mass originating from the 
cerebro-spinal fluid (Figs. 3, 7, 9), 2) numerous detached epithelial 
cells (Fig. 4), 3) blood corpuscles (Fig. 10) and occasionally 4) arti- 
facts formed from the fixing fluid. The first may assume a great 
variety of forms and appearances under the action of various fixing 
and staining agents. It may be diffuse, finely or coarsely granular 
(Fig. 3), in clot-like masses (Fig. 9), or sometimes aggregated about 
REISSNER’S fibre, whose course it may obscure and whose diameter 
it may appear to increase. Sometimes, especially in the ventricles, 
it becomes so coagulated about a blood corpuscle or some disintegrating 
epithelial cell as to produce artifacts strikingly like cells in appearance. 
In fact it would be possible to obtain photographs of such cell-like 
artifacts showing an apparent nucleus, a nucelolus, chromatin, and long 
streaming or branching dendritic processes. 
When such an artifact occurs about Rreissnmr’s fibre, it is easy to 
misinterpret it as a cell connected with the fibre. Artifacts due to the 
fixing fluids seldom occur except in the use of corrosive sublimate, and 
