st to the flame is
hottest, that farther away is cooler. By dropping water, toluol, xylol,
etc. on to it, one can fairly easily ascertain that point of the plate
which has reached the boiling temperature of the particular fluid.

Far more convenient is Victor Meyer's apparatus, used by chemists. This
consists of a copper boiler, modified for our purpose, with a roof of
thin copper-plate, perforated for the opening of the vapour tube. Small
quantities of toluol are allowed to boil for a few minutes in the
boiler, and the copper-plate soon reaches the temperature of 107 deg.-110 deg..

For the ordinary staining reagents (in watery fluids) it is enough to
place the air-dried preparation at about 110 deg. C. for one half to two
minutes. For differential staining mixtures, for instance the
eosin-aurantia-nigrosin mixture, a time of two hours is necessary, or
higher temperatures must be employed.

2. Chemical means.

_a._ To obtain a good triacid stain, the preparations may be hardened,
according to Nikiforoff, in a mixture of absolute alcohol and ether of
equal parts, for two hours. The beauty of specimens fixed by heat is
however not quite fully reached by this method.

_b._ Absolute alcohol fixes dried specimens in five minutes sufficiently
to stain them subsequently with Chenzinsky's fluid, or haematoxylin-eosin
solution. It is an advantage in many cases, especially when rapid
investigation is required, to boil the dried preparation in a test-tube
in absolute alcohol for one minute.

_c._ Formalin in 1% alcoholic solution was first used by Benario for
fixing blood preparations. The fixation is complete in one minute, and
the granulations can be demonstrated. Benario recommends this method of
fixing, especially for the haematoxylin-eosin staining.

These methods are described as the most suitable for
blood-investigation in general. For special purposes, for instance, the
demonstration of mitoses, blood platelets, etc., other hardening
reagents may be used with advantage: Sublimate, osmic acid, Flemming's
fluid, and so forth.

[gamma]. Staining of the dry specimen.

Staining methods may be classified according to the purpose to which
they are adapted.

We use first those which are suitable for a simple general view. For
this it is sufficient to use such solutions as stain haemoglobin and
nuclei simultaneously. (Haematoxylin-eosin, haematoxylin-orange).

Occasionally a stain is desirable which only brings ou