ed, but was unable to explain, has found a satisfactory solution
in Ehrlich's researches on the nucleated precursors of the myelocytes
and normocytes (see below).

The blood picture of the anaemias is made still more complicated in that
the diminutive cells do not preserve their normal shape, but assume the
well-known irregular forms: pear-, balloon-, saucer-, canoe-shapes.
Nevertheless in good dry preparations the smallest forms usually still
shew the central depression. The so-called "microcytes" constitute an
exception to this statement. These are small round forms, to which was
allotted in the early days of the microscopic investigation of the
blood, a special significance for the severe anaemias. They are however
nothing but contraction forms of the poikilocytes, as the crenated are
of the normal corpuscles. Consequently microcytes are but seldom found
in dried specimens, whilst in wet preparations they are easily seen
after some time. It is further of importance to know, that in fresh
blood the poikilocytes exhibit certain movements, which have already
given rise to mistakes in many ways. Thus at one time the poikilocytes
were considered to be the cause of malaria. More recently the somewhat
larger sizes were regarded by Klebs, Perles as amoebae and similar
organisms. In agreement with Hayem, who from the very first described
these forms as =pseudo-parasites=, a warning must be given against
attributing a parasitic character to them.

The origin of poikilocytosis, previously the subject of much
discussion, is now generally explained in Ehrlich's way. For the mere
fact, that by careful heating, poikilocytosis can be experimentally
produced in any blood, forces one to the assumption that the
poikilocytes are products of a fragmentation of the red blood corpuscles
("schistocytes," Ehrlich). And correspondingly the smallest fragments
shew the biconcave form in the dry specimen; for they too contain the
specific protoplasm of the disc "which possesses the inherent tendency
to assume the typical biconcave form in a state of equilibrium."

Qualitative changes in the protoplasm of the poikilocytes are not to be
observed, even by staining; and one may therefore ascribe to them
complete functional power, and regard their production as a purposeful
reaction to the diminished number of corpuscles. For by the division of
a larger blood corpuscle into a series of homologous smaller ones, the
respiratory surface is considerabl