, for which
they were characteristic, as pigment is for pigment cells, and glycogen
for cartilage cells (Neumann) and so forth. We can diagnose the
variously shaped mast cells only by the staining of their granules in
dahlia solution, that is by a microchemical test. And in the same way we
can separate tinctorially other granulated cells, morphologically
indistinguishable, into definite sub-groups. And for this reason, I
propose to call these granulations =specific=."

"The investigations were performed after Koch's method in the following
manner. The fluid (blood) or the parenchyma of the organs (bone-marrow,
spleen, etc.) was spread on cover-slips in as thin a layer as possible,
dried at room temperature, and after a convenient length of time
stained. I had chosen this apparently coarse method for the special
reason that for the histological recognition of new, possibly definite
chemical combinations, corresponding to the granulations, all substances
must be avoided that might act as solvents, _e.g._ water or alcohol, or
as oxydising agents, such as osmic acid. In this instance only such
procedures may be employed as will leave the simple drying of each
single chemical substance as much as possible unchanged."

A more detailed study of the process of staining, and of the relation
between chemical constitution and staining power, enabled a further
advance to be made. And the first result in this previously unworked
direction, was the sharp distinction between acid, basic, and neutral
dyes, and between the corresponding, oxy-, baso-, and neutrophil
granulations. The =triacid solution= was only found after trial of many
hundred combinations; and up to the present day this stain in its
original form or in slight modifications has played a prominent part in
various provinces of histology.

The classification of the cell-granules of the blood according to their
various chemical affinities which was drawn up by this method is
accepted to-day as the most valuable, and the only practical means of
grouping the leucocytes. From the first Ehrlich has insisted, =that
different kinds of cells possess different granules=, distinguished not
only by their tinctorial properties, but also by their various reactions
to solvents.

It is in this connection indeed, that Altmann's method, consisting of a
complicated hardening process, and the use of a single, always similar
stain, constitutes a retrograde step, in as much as it tends to