6 
GEORGE E. NlCllUELS. 
stiuuliiig, suffered accidental breakage prior to, or during, 
fixation. 
In tlic case of some of the larger animals, in order to 
ensure thorough penetration it was found necessary to 
remove part of the brain on one side. This was cut away 
with a razor, but only after partial hardening, in order to 
lessen the risk of crushing together the parts of the brain 
and the consequent disturbance or displacement of the fibre. 
Where })racticable, however, the brain was preserved entire, 
the removal of part being found to be necessary principally 
in the case of mammalian brains. 
Many different stains were employed, lleissner’s fibre 
being stained strongly by several of these. It is brought out 
especially well after fixation in aceto-bichromate by heavily 
staining in bulk in Grenadier’s borax-carmine, followed, upon 
the slide, by picro-indigo-carmine. This latter stain was pre- 
pared by mixing one part of a saturated solution of picric acid 
in 70 per cent, alcohol with two parts of a saturated solution of 
indigo-carmine in 70 per cent, alcohol. Sections immersed for 
about five minutes in this solution become considerably over- 
stained. This excess of stain is got rid of by washing in a 
number of changes of 70 jjer cent, alcohol till all trace of free 
])icric acid is removed. (If the washing be not thorough the 
lesidual jiicric acid begins to crystallise out in a few days.) 
Sections treated in this way usually show axis-cylinders 
stained red, with medullary sheaths green, while Eeissner’s 
fibre appears of a dull purple tint. Nerve-cells stain 
variously, the nuclei of all being particularly well brought 
out, while the cytoplasm, in most cases, is only lightly stained; 
in the “ Dachkern ” cells, however, the cytoplasm becomes 
well stained, and takes on a reddish or purplish tint. Blood- 
corpuscles are stained green. 
If the washing in 70 per cent, alcohol has been prolonged, 
Keissner’s fibre fades to a pale blue or blue-green colour, and 
connective tissues a])pear bright blue. 
Another stain which has given me good results is iron- 
bi azilin used as descilbed by Ilicksou (’Ul). yome especially 
