300 JOURNAL OF COMPARATIVE NEUROLOGY. 
results with the Pat decolorization unless osmic acid is used as 
indicated below (£). 
(2) Iron alum did not prove to bea valuable mordant— 
except where used asa hardening reagent for the peripheral 
nerves as above described. It was still worse as a decolorizer. 
(¢) Mordanting the celloidin block zx ¢ofo without further 
mordanting does not give such brilliant preparations as when 
the celloidin sections are mordanted instead. 
(7) No constant differences were noted between the WEI- 
GERT alkaline haematoxylin and the neutral haematoxylin. Cer- 
tainly with the Pat decolorization the neutral is as good or possi- 
bly somewhat better. 
(£) A slight or considerable increase in the brilliancy of 
WEIGERT-PAL preparations can often be obtained by dipping 
the sections in osmicacid for a fraction of a minute immediately 
after they have been removed from haematoxylin and rinsed in 
water. When this is done, sections mordanted in copper acetate 
before staining will often give good results with the Pat decolor- 
ization, though otherwise, as indicated above (g), they would be 
useless for this method. 
Osmic, used in this way before the borax-ferricyanide decol- 
orization always gave poor results. 
(7) The time of mordanting and staining is omitted in A, 
B and C for purposes of condensation. When the time devoted 
to these processes has been too short, the stain is too pale and 
the finer fibers are not be well demonstrated; when too long, de- 
colorization is too protracted and the ground will not be suffi- 
ciently decolorized or the fibers will be over-decolorized. Nat- 
urally, the longer the mordantage the shorter the time required 
for staining. Usually, at the temperature of the room, about 
12 hrs. for mordanting and about 4 to 6 hrs. for staining were the 
most favorable, but no rule can be laid down, owing to the 
condition of the material and other factors. Heat will of course 
accelerate the process but this is not necessarily to be recom- 
mended, it being liable, especially when mordanting with copper 
bichromate, to render the sections brittle. 
Dept. of Zoology, . 
Nov., 1903. 
