STRUCTURE AND DEVELOPMENT OE REISSNER’s ElBRE. 7 
satisfactory results have been obtained by the use of this 
stain with brains of Petromyzon which liad been fixed in 
aceto-bichromate, the nerve-fibres being wonderfully defined. 
It is, indeed, particularly useful for material where the fibres 
are non-medullated. 
Various hgematoxylin stains were also tried, and generally 
served to bring out Reissner’s fibre well. Ehrlich’s acid- 
haeinatoxylin stains the fibre strongly, and Ueidenhain’s iron- 
htematoxylin upon aceto-bichromate material in particular 
yields very satisfactory results. A modification of Weigert’s 
method, suggested by C. J. llerrick, was tried upon material 
fixed in aceto-bichromate as well ,as upon material fixed in 
Flemming’s stronger fluid and in Zenker’s fluid ; in eveiy case 
Reissner’s fibre was found to take the stain strongly, but was 
readily decolorised by any of the several decolorising fluids 
commonly employed. 
Asa test for elastin, both (Jnna’s orcein stain and Weigert's 
elastin stain, which were brought to my notice by Professor 
Dixon, were tried upon the fibre in the spinal cord of the frog, 
and with both reagents the fibre became stained, but lightly. 
The metliylene-blue stain recommended by Ramsey (’01) 
was employed upon both 'I’eleost and Elasmobrauch brains. 
It was observed that Reissner’s fibre took up the stain cpiite 
well, but unfortunately the stain appears to be transient. 
The rapid method of Golgi was tiled upon Elasmobrauch 
material (Paia, Scyllium), and although quite satisfactory 
general impregnations were obtained, I found, as apparently 
all previous observers have done, that Reissner’s fibre in- 
variably fails to become impregnated. This fact has been 
explained by Sargent as probably due to the presence of 
much non-dialisable colloid material in the cerebro-spiual 
fluid Avhich surrounds the fibre, which was supposed to inter- 
fere with the action of the fixing fluid. Accordingly, in 
])reparing some Selachian material for this method, I removed 
about one third of the brain by a longitudinal vertical cut, 
thus partly exposing the ventricles and allowing the cerebro- 
spinal fluid to drain away, but Reissuer’s fibre did not even 
