.298 JOURNAL OF COMPARATIVE NEUROLOGY. 
It is a question whether the plain bichromate fixing and harden- 
ing be not superior in some regards. 
(0) Formalin fixed and hardened material will apparently 
keep indefinitely in formalin and yet be capable of giving fine 
WEIGERT preparations when subjected to the appropriate treat- 
ment (vida supra, F). Asa corollary to this it would appear 
advisable to keep all material to be used for WEIGERT prepara- 
tions, however fixed and hardened, in formalin instead of alco- 
hol. Material kept long in alcohol will not usually yield brilliant 
WEIGERT preparations. 
It may be well to call attention here to the fact that sec- 
tions already stained for WEIGERT but not decolorized may often 
be kept for months in water containing some formalin (to pre- 
vent the growth of molds etc.) and yet give good preparations 
when decolorized. This proved to be the case with some sec- 
tions prepared as indicated above under F (2). There is appar- 
ently a very slight gradual loss in brilliancy. Sections stained 
asin F (2) and kept thus 1%-yrs. in 10% + formalin still 
yielded good preparations when decolorized. Some of these 
which had been brought, after rinsing in water, into formalin 
and the formalin changed when discolored were practically in- 
distinguishable, when decolorized, from those decolorized im- 
mediately after staining. 
(c) Material fixed and hardened in formalin should in all 
cases be mordanted: zz Zofo before bringing it into alcohol pre- 
paratory to imbedding. Here lies the explanation, probably, 
of the discrepancy between the results obtained with formalin 
material by Borron' and those obtained by HErrIck.? BoLTon 
mordanted sections made from frozen or gum imbedded material, 
while HErrRIcK mordanted paraffine sections. It is also better 
to mordant pieces of the material immediately before they 
are to be used so that mordanted blocks need not be kept long 
before cutting and staining. 
It is probable, from this, that some of the apparently bad 
fixation of ‘medullated nerve fibers seen at times in formalin 
material is really due more to the subsequent treatment, the 
1 Journ, Anat. Physiol. Vol. XII, N. S., 1898. 2 Op. cit. 
