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 considerably increased.
C. A third morphological variation which anaemic blood may shew in the
more severe degrees of the disease, is the appearance of =nucleated red
blood corpuscles=.
Though we do not wish to enter here upon the latest questions concerning
the origin of the blood elements, we must shortly indicate the present
state of our knowledge of the nucleated red corpuscles.
Since the fundamental work of Neumann and Bizzozero, the nucleated forms
have been generally recognised as the young stages of the normal red
blood corpuscles. Hayem's theory, on the contrary, obstinately asserts
the origin of the erythrocytes from blood-platelets, and has, excepting
by the originator and his pupils, been generally allowed to drop.
Ehrlich had in the year 1880 pointed out the clinical importance of the
nucleated red blood corpuscles, in as much as he demonstrated that in
the so-called secondary anaemias, and in leukaemia, nucleated corpuscles
of the normal size, "normoblasts"; in pernicious anaemia excessively
large elements, "megaloblasts," "gigantoblasts" are present. At the same
time Ehrlich mentioned that the megaloblasts also play a prominent part
in embryonic blood formation.
In 1883 Hayem likewise proposed a similar division of the nucleated red
blood corpuscles into two,
(1) the "globules nuclees geantes" which he found exclusively in the
embryonic state, (2) the "globules nuclees de taille moyennes" which he
found invariably present in the later stages of embryonic life, and in
adults. Further, W. H. Howell (1890) found in cats' embryoes two kinds
of erythrocytes, (1) very large, equivalent to the blood cells of
reptiles and amphibia ("ancestor corpuscles"), and (2) of the usual size
of the blood corpuscles of mammalia. And similarly more recent authors,
H. F. Mueller, C. S. Engel, Pappenheim and others, have adhered to the
division of haematoblasts into normo- and megaloblasts. And it is on the
whole recognised, that, physiologically, normoblasts are always present
in the bone-marrow of adults, as the precursors of the non-nucleated
erythrocytes; that the megaloblasts, however, are never found there
under normal circumstances, but only in embryonic stages, and in the
first years of extra-uterine life.
S. Askanazy on the contrary has expressed the view, that the normoblasts
may arise from the megaloblasts, and thereby denies the principal
distinction between them. Schaumann also holds that the separation of
the two kinds rests on doubtful foundation, since occasionally it is
questionable whether particular cells are the normoblasts or the
megaloblasts.
We distinguish three kinds of nucleated red blood-corpuscles on the
grounds of the following characters;
1. =The normoblasts.= These are red corpuscles of the size of the usual
non-nucleated disc, whose protoplasm as a rule shews a pure haemoglobin
colour, and which possess a nucleus. Occasionally there may be 2-4
nuclei. The sharply defined nucleus lies generally in the centre,
comprises the greater part of the cell, and is above all distinguished
by its intense colour with nuclear stains, which exceeds that of the
nuclei of the leucocytes, and indeed of all known nuclei. This property
is so characteristic that the free nuclei, which occur occasionally in
anaemias, and particularly often in leukaemia, may be recognised as nuclei
of normoblasts, although surrounded by traces only of haemoglobin, or by
none at all.
2. =The megaloblasts.= These are 2-4 times as large as normal red blood
corpuscles. Their protoplasm, which constitutes by far the chief portion
of the body of the cell, very often shews anaemic degeneration to a
greater or less degree. The nucleus is larger than that of the
normoblasts, but does not form so considerable a fraction of the cell as
in the latter. It is often not sharply defined, and is of a rounded
shape. It is distinguished from the nucleus of the normoblast by its
much weaker affinity for nuclear stains, which may often be so small
that little practised observers perceive no nucleus.
Occasionally very large cells are present of the kind just described,
which are therefore called =gigantoblasts=, but which are not
distinguishable in other respects from the megaloblasts.
It cannot be denied that it is often difficult to decide whether a
particular cell is to be regarded as a specially small megaloblast or a
large normoblast. In such cases one would naturally search the
preparation for perfect forms of haematoblasts, and for the presence of
free nuclei or of megalocytes, in order to obtain an indirect conclusion
concerning the cells in question.
3. =The microblasts.= These are occasionally present, _e.g._ in traumatic
anaemias, but they are very seldom found, and have not so far attracted
particular attention.
* * * * *
The question of the meaning of the =normoblasts= and =megaloblasts= has led
to lively and significant discussions, partly in favour of, partly
against the distinction between these two cell forms. After surveying
the literature, we are forced to separate the megaloblasts from the
normoblasts, in the first place because of their subsequent histories,
and the peculiarities of their nuclei, and secondly because of clinical
observation.
[alpha]. =The fate of the nuclei.= For some time past two views, almost
diametrically opposed, have been in existence with regard to the nature
of the change of the nucleated to the non-nucleated erythrocytes. The
chief exponent of the one, Rindfleisch, taught that the nucleus of the
erythroblasts leaves the cell, which thereby becomes a complete
erythrocyte, whilst the nucleus itself, by the aid of the small remnant
of protoplasm which surrounds it, takes up new material from the
surrounding plasma, manufactures haemoglobin and so becomes a fresh
erythroblast. According to the second theory the erythroblasts change
to non-nucleated discs by the destruction and solution of the nucleus
within the cell body. ("Karyorrhexis," "Karyolysis.") The authors who
support this view and also describe it as the only kind of erythrocyte
formation are chiefly Koelliker and E. Neumann.
Rindfleisch arrived at his theory by direct observation of the process
described, as it occurred in physiological saline solution with the
blood of foetal guinea-pigs and teased preparations of bone-marrow.
E. Neumann regards Rindfleisch's doctrine as untenable, since the
process which he observed is chiefly the result of a severe injury of
the blood from the sodium chloride solution and the teasing. If a method
of preparation be chosen which protects the blood as far as possible,
and avoids every chemical and physical alteration, the exit of the
nucleus as described by Rindfleisch does not occur.
The view of Koelliker and Neumann that the nuclei gradually decay in the
interior of the cell is not supported by the observation of a process,
but by the fact that in suitable material, for instance, foetal
bone-marrow, liver blood, and leukaemic blood, the transition from
erythroblast to erythrocyte is shewn by all phases of nuclear
metamorphosis. v. Recklinghausen professes to have directly observed the
dissolution of the nucleus within the cell in rabbit's blood, kept
living in a moist chamber. Pappenheim's opinion however, that in this
case processes are concerned such as Maragliano and Castellino have
described as artificial necrobiosis, seems in this connection worthy of
consideration.
Just as with regard to the formation of erythrocytes the views differ
one from another, so also with regard to the "free" nuclei which come
under observation in numerous preparations. Koelliker has taught that
these nuclei are not quite free, but are always surrounded by a minute
border of protoplasm. On the other hand Rindfleisch regards these nuclei
as having migrated from, or having been cast off by the erythroblasts;
and Neumann explains them as the early forms of erythroblasts. Ehrlich
was the first to endeavour to effect a compromise between the directly
opposed views of Rindfleisch and Neumann. He taught that both kinds take
part in the production of the red discs. From blood preparations which
contain numerous normoblasts, for instance in "blood crises" (see p.
62), an unbroken series of pictures can easily be put together shewing
how the nucleus of the erythroblast leaves the cell, and at last
produces the appearance of the so-called free nucleus. It must be
expressly mentioned that these pictures are only to be found in
specimens in whose preparation pressure of any kind upon the blood has
been avoided. Further, however rich a blood may be in normoblasts, the
metamorphosis of the nucleus as described by Neumann, is practically
never to be observed. It is quite otherwise with the megaloblasts.
Amongst them, few examples are to be found in which traces at least of
the destruction and solution of the nucleus are not shewn, and in a
blood preparation of pernicious anaemia, which is not too poor in
megaloblasts, one can construct step by step the unbroken series from
megaloblasts with a complete nucleus through all stages of Karyorrhexis
and Karyolysis to the megalocytes, as the process is described by
Neumann[9].
From Ehrlich's observations it follows, that the normoblasts become
normocytes by extrusion or emigration of the nucleus, the megaloblasts
become megalocytes by degeneration of the nucleus within the cell.
M. B. Schmidt without making use of the principal distinction made by
Ehrlich, also concludes from his researches on sections of the
bone-marrow of animals in extra-uterine life, that both kinds of
erythrocyte formation occur.
Quite recently Pappenheim, partly in conjunction with O. Israel, has
carried out very thorough researches on these particular points. As the
subject for observation he chose the blood of embryonic mice. He was
able in the first place, like Rindfleisch, to produce the exit of the
nuclei from the cells by the addition of "physiological" salt solution
to fresh blood, and is of the opinion that the exit of the nucleus from
the erythroblasts only takes place artificially.
In embryonic blood the metamorphosis to erythrocytes occurs exclusively
by nuclear destruction and solution within the cell, be it in the case
of megalo- or gigantoblasts or of cells of the size of the normal red
blood corpuscle.
The free nuclei that are observed, whose appearance Pappenheim explains
by a preceding solution of the protoplasm (plasmolysis), he regards, in
opposition to Rindfleisch and Neumann, not as the beginnings of a
developmental series, but as the surviving remnants of the degenerated
dying blood cells. Clinical observation, certainly, does not support
this conception of Pappenheim's; in as much as in suitable cases with
numerous free nuclei (leukaemia, blood crises) transitional forms, which
according to Pappenheim must necessarily be present, are not to be
found. Moreover, in alluding to a case of leukaemia of this kind, this
author himself admits that the appearance of free nuclei can be
explained in this instance by the exit of the nucleus.
Although Pappenheim, as above mentioned, recognises no difference
between megaloblasts and normoblasts in embryonic blood as far as the
fate of the nucleus is concerned, he nevertheless decidedly supports
Ehrlich's separation of the erythroblasts into these two groups, as two
haematogenetically distinct species of cells. He does not regard as
distinguishing characteristics, the size and haemoglobin content of the
cells--although as we have described above, these are in general
different in normo- and megaloblasts--for these two properties undergo
such great variations as to increase considerably under certain
circumstances the difficulty of diagnosis of individual cells. The chief
characteristic is, as Ehrlich has always particularly insisted, the
=constitution of the nucleus=. The nuclei of cells which are with
certainty to be reckoned among the normoblasts are marked by the absence
of structure, their sharply defined contour, their intense affinity for
nuclear stains. That is by properties which histology sums up under the
name =Pyknosis= (Pfitzner) and recognises as signs of old age. The nuclei
of the megaloblasts are round, shew a good deal of structure, and stain
far less deeply.
[beta]. The clinical differences. Normoblasts are found almost
invariably in all severe anaemias that are the result of trauma,
inanition or organic disease of some kind. They are however mostly
rather scanty, so that a preparation must be searched for some time
before an example is found. But occasionally, most often in acute, but
also in chronic anaemias, and even in =cachectic= conditions, every field
shews one or more normoblasts.
V. Noorden was the first to describe a case in which in the course of a
haemorrhagic anaemia normoblasts temporarily appeared in such overwhelming
numbers in the circulating blood, that the microscopic picture, which at
the same time comprised a marked hyperleucocytosis, was almost similar
to that of a myelogenous leukaemia. And as in addition to this occurrence
the number of blood corpuscles was nearly doubled, v. Noorden gave it
the distinctive name "blood crisis."
The following procedure is to be recommended for the
investigation of the blood crisis:
1. Estimation of the absolute number of red blood corpuscles.
2. Estimation of the proportion of white to red corpuscles.
3. Estimation of the proportion of nucleated red to white
corpuscles by means of the quadratic ocular diaphragm (see page
31) in the dry preparation.
For instance if we find in a case of anaemia, 3-1/2 millions of
red blood corpuscles, the proportion of white to red corpuscles
= 1/100 and that of the nucleated red to the white = 1/10, then
in 1 cubic millimeter there are 3500 nucleated red corpuscles,
that is for 1000 ordinary there is 1 nucleated corpuscle.
=Megaloblasts= on the contrary are never found in traumatic anaemias. And
in chronic anaemias of the severest degree, the result for example of old
syphilis, carcinoma of the stomach and so forth, one looks for them
almost always in vain, although they are sometimes to be found in
leukaemia. On the contrary, the conditions, apparently much milder, in
which from the clinical history, aetiology and general objective symptoms
pernicious anaemia is suggested, are almost without exception
characterised by the appearance of megaloblasts in the blood.
Nevertheless in very late stages of the disease they are always scanty,
and a very tedious search through one or more specimens is often
required to demonstrate their presence. Hence follows the rule, that the
investigation of a case of severe anaemia should never be considered
closed, before three or four preparations at least have been minutely
searched for megaloblasts under an oil immersion objective.
This clinical difference between the two kinds of haematoblasts admits of
but one natural conclusion, which primarily leaves untouched the
question, so much discussed at the present time, whether the megalo- or
normoblasts can change one to the other. In all cases of anaemia, in
which the fresh formation occurs according to the normal type, only in
greater quantity and more energetically, we find normoblasts. Almost all
anaemias resulting from known causes: acute haemorrhages, chronic
haemorrhages, poverty of blood from inanition, cachexias, blood poisons,
haemaglobinaemia and so forth,--in short all conditions rightly called,
secondary, symptomatic anaemias,--may shew this increase of normal blood
production. In the conditions, which Biermer, on the grounds of their
clinical peculiarities, has distinguished as "essential, pernicious
anaemia" megaloblasts on the contrary occur, and represent an embryonic
type of development. The extent to which this type participates in the
blood formation in pernicious anaemia is most simply demonstrated by the
fact that megaloblasts are present in all cases of pernicious anaemia, as
Laache first shewed, and in some cases form the preponderating portion
of the blood discs. Whilst, therefore, in the ordinary kinds of anaemia
we find that the red corpuscles tend to produce small forms, in
pernicious anaemia, on the other hand, and exclusively in this form, we
find a tendency in the opposite direction. This constant difference
cannot be a chance result, but must depend on some constant law: in
pernicious anaemia excessively large blood corpuscles are produced.
Ehrlich's demonstration of megaloblasts has sufficed for this logical
advance. =All researches, which try to obscure or totally deny the
distinction between megaloblasts and normoblasts are wrecked by the
simple clinical fact that in pernicious anaemia the blood is
megaloblastic.=
The appearance of megaloblasts and megalocytes is therefore evidence
that the regeneration of the blood in the bone-marrow is not proceeding
in the normal manner, but in a way which approximates to the embryonic
type. The extreme cases are naturally seldom, such as that of
Rindfleisch, in which the whole bone-marrow was found full of
megaloblasts. It is sufficiently conclusive for the pernicious 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 is so unequivocal, that it is a
matter of surprise that Askanazy chooses to deduce from it, the ready
transition from megaloblasts to normoblasts; whereas it is clear and
definite evidence that =megaloblasts are only produced under the
influence of a specific intoxication=. And in this way the presence of
megaloblasts in the pernicious anaemias is to be explained. The
megaloblastic degeneration of the bone-marrow depends on the presence of
certain injurious influences, of which unfortunately we are as yet
ignorant. Were it possible to remove them, it is quite certain _a
priori_ that the bone-marrow--if the disease were not too
advanced--would resume its normal normoblastic type of regeneration.
Clinical observation supports this contention in many cases. In
megaloblastic anaemias apparent cures are by no means rare, but sooner or
later a relapse occurs, and finally leads with certainty to a lethal
issue. These cases, familiar to every observer, prove with certainty
that the megaloblastic degeneration as such may pass away, and that in
isolated cases the conventional treatment by arsenic suffices to bring
about this result. A definite cure however under these conditions is not
yet attained, since we do not know the aetiological agent, still less can
we remove it. =For this reason, the prognosis of megaloblastic anaemia,
apart from the group of Bothriocephalus anaemia, is exceedingly bad.=
FOOTNOTES:
[8] Dunin, on the contrary, designates the appearance of nucleated red
blood corpuscles within the first 24 hours after the loss of blood as
normal and regular. This view does not correspond with the facts. A
single case on one occasion may exhibit a rarity of this kind.
[9] Probably the dot-like and granular enclosures in the red corpuscles,
which stain with methylene blue, and which Askanzy and A. Lazarus have
observed in numerous cases of pernicious anaemia are also products of a
similar nuclear destruction.
[10] It does not seem superfluous in this place expressly to emphasise,
that what has been said on the diagnostic importance of the megaloblasts
only holds for the blood of adults. For the conditions of the blood in
children, which vary in many respects from that of adults see "Die
Anaemie," Ehrlich and Lazarus, Pt. II. (Anaemia pseudoleukaemica infantum).
THE WHITE BLOOD CORPUSCLES.
The physiological importance of the _white blood corpuscles_ is so many
sided that they form the most interesting chapter of the subject. That
the white corpuscles play a significant part in the physiology and
pathology of man has been recognised but slowly, obviously because there
was at first some hesitancy in ascribing important functions to elements
that are present in the blood in such relatively small numbers. A place
in pathology was first assured to them by Virchow's discovery of
leukaemia. The interest in the question was increased by Cohnheim's
discovery that inflammation and suppuration are due to an emigration of
the white blood corpuscles, and these conditions were particularly
suitable for throwing light on normal processes. The fact that in
diffuse inflammations, large quantities of pus are often produced in a
short time, without the blood being thereby made poorer in
leucocytes,--that the opposite indeed occurs,--necessitated the
supposition that the source of the leucocytes must be extraordinarily
productive. Hence in contradistinction to the red blood corpuscles,
their small number is fully compensated by their exceptional power of
regeneration.