COAL-TAR COLOURS IN GENERAL               107
thus rendering necessary special precautions for the preser-
,vation of stained specimens. Very few of these dyes natu-
Erally give a nuclear stain, so that such a stain can only be
obtained by means of a special method of washing out-the
Bdttcher-Hermann process, of which, as explained and modi-
fied by Flemming, I proceed to give an account. This is fol-
lowed by an account of Griesbach's examination of various
anilin colours not studied by Flemming, and that, again, is
followed by special paragraphs devoted to some other im-
portant anilin stains, which will conclude this part of the
matter; the subject of double staining being treated sepa-
rately.
From an examination of the literature abstracted in this
chapter it must be concluded that very few of the anilin
stains at present known are capable of being useful to the
morphologist-to the pathologist they may be of far greater
:importance. At Naples only two anilins are generally em-
ployed, viz. Bismarck brown and safranin. The worker at
morphology will probably find the following stains sufficient
for all his needs, viz. as nuclear stains, iodine green, methyl
green, Bismarck brown, safranin; whilst anilin blue is
sometimes useful as a diffuse stain for rendering visible very
delicate membranes, transparent chitinous structures and the
like, either as a single dye, or used after a carmine stain to
produce a double stain.
136. Anilin Staining for Nuclei (Bbttcher's and Hermann's
method').-I take the following from a paper by Flemming,
1. c.:
It was made out independently by Bottcher and by Her-
mann that by washing out with alcohol the diffuse stain of
anilin or "nitro-colours," clearing with oil of cloves, and
mounting in balsam, a fine nuclear and permanent stain may
be obtained. That which makes this method peculiarly valu-
able is that it enables us to obtain permanent preparations of
1 'Arch. Mik. Anat.,' xix (1881), pp. 317 and 742.

MR