r the
majority of the granules. Ehrlich was able by the aid of this dye to
demonstrate granules, even in some vegetable cells. Moreover the method
of using it is the simplest conceivable, as subcutaneous or intravenous
injection, or even feeding, in the higher animals stains the granules;
with frog's larvae and invertebrates, to allow them to swim in a dilute
solution of the dye is often sufficient. The staining also succeeds in
"surviving" organs, and is best effected by allowing small pieces to
float in physiological salt solution, to which a trace of neutral red is
added, under plentiful access of air. When the object is macroscopically
red it is ready for examination.

The finest results are naturally given by organs that are easily teased
out, _e.g._ flies' eggs, or the Malpighian canals of insects. The
staining solution is to be chosen so that the act of staining does not
last too long, but on the other hand too high a concentration must not
be used. About 1/50000 to 1/100000 is recommended, so that the
protoplasm and nucleus remain quite uncoloured. Artificial products with
this method cannot entirely be excluded, and, _e.g._ in plant-cells
containing tannin, are to be explained by the production and
precipitation of the salt of tannic acid. However it is not difficult
for the experienced to recognise artificial products as such in
individual cases. The kind of granulation, the typical distribution, a
comparison with neighbouring cells, the combination of various methods,
the comparison of the same object under vital and "=survival=" staining,
facilitate judgment and obviate mistakes of this kind.

The majority of the granules of vertebrates are stained orange-red by
neutral red, corresponding with the weakly alkaline reaction of these
forms. Granules staining in pure fuchsin colour and which hence possess
a weak acid reaction are much more rarely found.

Combination staining may be recommended as a valuable aid to the neutral
red method. Ehrlich has used a double stain with neutral red and
methylene blue. Frog's larvae were allowed to remain in a solution of
neutral red, to which a trace of methylene blue had been added. He then
found red granulations almost exclusively, only the granules of the
smooth musculature of the stomach were stained intensely blue. With the
aid of a threefold combination Ehrlich obtained a still further
differentiation of the living cell-granules. There is no doubt whatever
that a th