ernicious nature of
the case, "if only considerable portions but not the whole marrow, have
lapsed into megaloblastic degeneration." We can now say that the
megaloblastic metamorphosis is not a purposeful process, and for the
following reasons: 1. Since the fresh formation of red blood corpuscles
by means of the megaloblastic method is clearly much slower. This is
especially borne out by the fact that the megaloblasts are present in
the blood always in small numbers only, whilst the normoblasts, as above
mentioned, are often found in much larger quantities. In agreement with
this, "blood crises" are not to be observed in the megaloblastic
anaemias. 2. Since the megalocytes which are formed from the megaloblasts
possess in proportion to their volume a relatively smaller respiratory
surface, and so constitute a type disadvantageous for anaemic
conditions[10]. This is still more evident when we remember that the
production of poikilocytes is on the contrary a serviceable process.

The megaloblastic degeneration of the bone-marrow is no doubt due to
chemical influences, which alter the type of regeneration in a
disadvantageous manner. We do not for the most part yet know the
exciting causes of the toxic process; consequently we are unable to put
a stop to it, and its termination is lethal. The Bothriocephalus
anaemias, which in general as is well-known offer a good prognosis, by no
means contradict this view. They hold their privileged position amongst
the anaemias of the megaloblastic type, only for the reason that their
cause is known to us, and can be removed. As in many infectious
diseases, individuals react quite differently to the presence of the
Bothriocephalus. Some remain well; others show the signs of simple
anaemia, ultimately with normoblasts; whilst a third group presents the
typical picture of pernicious anaemia. For many years, so long as its
aetiology was unknown, Bothriocephalus anaemia was not separated on
clinical grounds from pernicious anaemia. Severe Bothriocephalus anaemia
may be described as a pernicious anaemia, with a known and removable
cause. Good evidence for this point of view is afforded by a case of
Askanazy, who describes a severe pernicious anaemia, with typical
megaloblasts, in which after the complete expulsion of the
Bothriocephalus, the megaloblastic character of the blood formation
quickly vanished, was replaced by the normoblastic, and the patient
rapidly recovered. This observation i