that started from Cohnheim, bore fruit for clinical histology. As we
have mentioned this was due to the circumstance that an exact
differentiation of the various forms of leucocytes was very difficult
with the methods in use up to that time. Although such distinguished
observers as Wharton Jones and Max Schultze had been able to distinguish
different types of leucocytes, Cohnheim's work remained clinically
fruitless since the criteria they assigned were far too subtle for
investigation at the bedside. Virchow indeed, the discoverer of
leucocytosis, interpreted it as an increase of the lymphocytes; whereas
it is chiefly produced by the polynuclear cells. Only after the
distinction was facilitated by the dry preparation and the use of
stains, did interest in the white corpuscles increase, and continue
progressively to the present day. This is borne out by the exceptionally
exhaustive haematological literature, and particularly by that of
leucocytosis.
In spite of these advances, a retrograde movement in the doctrine of the
leucocytes has gained ground surprisingly, especially in the last few
years. Ever since Virchow's description of the lymphocytes, observers
have tried to separate the various forms of leucocytes one from another,
and if possible to assign different places of origin to these different
kinds. There now suddenly appears an endeavour to bring all the white
blood corpuscles into one class, and to regard the different forms as
different stages merely of the same kind of cells. The following
sections will show that this tendency is unwarranted and unpractical.
I. NORMAL AND PATHOLOGICAL HISTOLOGY OF THE WHITE BLOOD CORPUSCLES.
The classification of the white corpuscles of normal human blood, drawn
up by Ehrlich, has been accepted by most authors, and we therefore give
a short summary of it, as founded on the dry specimen.
1. =The Lymphocytes.= These are small cells, as a rule approximating in
size to the red blood corpuscles. Their body is occupied by a large
round homogeneously stained nucleus centrally situated, whilst the
protoplasm surrounds the nucleus as a concentric border. Between nucleus
and protoplasm there is often found a narrow areola, which doubtless
results from artificial retraction. Nucleus and protoplasm are basophil,
nevertheless in many methods of staining the protoplasm possesses a much
stronger affinity for the basic stain than does the nucleus. The nucleus
in these cases stands out as a bright spot from the deeply stained mass
of protoplasm, which is reticulated in a peculiar manner.
Within the nucleus are often to be found one or two nucleoli with a
relatively thick and deeply stained membrane. With methylene blue and
similar dyes the protoplasm stains unequally, which is not to be
considered as the expression of a granulation, as Ehrlich first
assumed, but rather of a reticular structure. The contour of the
lymphocytes is not quite smooth as a rule, at least in the larger forms,
but is somewhat frayed, jagged, and uneven (Fig. 1). Small portions of
the peripheral substance may repeatedly bud off, especially in the large
forms, and circulate in the blood as free elements. In stained
specimens, especially from lymphatic leukaemia, these forms, which
completely resemble the protoplasm of the lymphocytes in their staining,
may from their nature and origin be readily recognised.
As far as the further metamorphosis of the nucleus is concerned, a sharp
notching of the border of the nucleus may occasionally be found, the
further fate of which is shewn in the accompanying figure (Fig. 3). It
is evident that in this case the resulting nuclear forms are quite
different from those which are characteristic of the polynuclear
elements.
The protoplasm possesses no special affinity for acid and neutral dyes,
and hence in triacid and haematoxylin preparations the small lymphocytes
are seen chiefly as lightly stained nuclei, apparently free. In the
larger cells the protoplasm can be seen even in these preparations to be
slightly stained. By the aid of the iodine-eosine method the reaction of
the protoplasm of the lymphocytes is shewn to be strongly alkaline. They
do not contain glycogen.
These properties taken as a whole constitute a picture completely
characteristic of the lymphocytes; and these elements can thereby be
diagnosed and separated from other forms, even when their size varies.
Generally speaking, these cells, as above mentioned, are distinguished
in the blood of the healthy adult by their small size, approximating to
that of the red blood corpuscles. In the blood of children on the
contrary larger forms are found even in health; and in lymphatic
leukaemia particularly large forms occur, which are mistaken in various
ways by unpractised observers. Thus Troje's "marrow cells" still figure
in the literature, but have absolutely nothing to do with the marrow.
They are large lymphocytes, as was established by A. Fraenkel years
afterwards.
[Illustration: Fig. 1.
Fraying out of the protoplasmic border in large lymphocytes. Free plasma
elements formed by budding. ("Plasmolysis.")
(From a photograph of a preparation from chronic lymphatic leukaemia.)
_To face page 72_]
[Illustration: Fig. 2. (From Rieder's Atlas.)
Metamorphosis of the nucleus of the lymphocytes. (Combined picture from
a preparation from acute leukaemia.)
_To follow Fig. 1_]
In the normal blood of adults the number of the lymphocytes amounts to
about 22-25% of the colourless elements.
Increase of the lymphocytes alone occurs, but in comparison with that of
the other forms, much more seldom, and will be conveniently called by
the special names of "lymphocytosis" or "lymphaemia."
2. Sharply to be distinguished from the lymphocytes is the second group:
the "large mononuclear leucocytes." These are large cells about twice to
three times the size of the erythrocytes. They possess a large oval
nucleus, as a rule eccentrically situated and staining feebly, and a
relatively abundant protoplasm. The latter is free from granulations,
feebly basophil, and in contrast to the protoplasm of the lymphocytes
stains less deeply than the nucleus. This group is present in normal
blood in but small numbers (about 1%). They are separated from the
lymphocytes because they are totally different in appearance, and
because forms transitional between the two are not observed. It cannot
yet be decided from which blood-producing organs these forms arise,
whether from spleen or bone-marrow, although there are many reasons for
regarding the latter as their place of origin.
These large mononuclear leucocytes change in the blood to the following
kind:
3. "=The transitional forms.=" These resemble the preceding, but are
distinguished therefrom by deep notchings of the nucleus, which often
give it an hour-glass shape, further by a somewhat greater affinity of
the nucleus for stains, and by the presence of scanty neutrophil
granulations in the protoplasm. The groups 2 and 3 comprise together
about 2-4% of the white blood corpuscles[11].
4. The (so-called) "=polynuclear leucocytes=." These arise in small part,
as will be described later in detail, from the above-mentioned No. 3,
within the blood stream. By far the larger part is produced fully formed
in the bone-marrow, and emigrate to the blood. These cells are rather
smaller than Nos. 3 and 2 and are distinguished by the following
peculiarities: firstly by a peculiar polymorphous form of nucleus which
gives the relatively long, irregularly bulged and indented nuclear rod
the appearance of an S, Y, E or Z. The complete decomposition of this
nuclear rod into three to four small round single nuclei may occur
during life, as a natural process. Ehrlich first discovered it in a case
of haemorrhagic small-pox; it is frequently found in fresh exudations.
Formerly when various reagents, for instance acetic acid, were
customarily used, the decomposition of the nucleus into several parts
was more frequently observed, and Ehrlich for this reason chose the not
wholly appropriate name "polynuclear" for this form of cell. As this
name has now been universally adopted, and misunderstandings cannot be
expected, it is undoubtedly better to keep to it. The expression "Cells
with polymorphous nuclei" would be more accurate.
[Illustration: Fig. 3.
Nucleoli in larger lymphocytes.
(From a photograph of a preparation from chronic lymphatic leukaemia.)
_To face page 74_]
The nucleus stains very deeply with all dyes; the protoplasm possesses a
strong attraction for most acid stains, and is unmistakeably
characterised by the presence of a dense neutrophil granulation. The
reaction of the protoplasm is alkaline, to a less degree however than in
the lymphocytes. No free glycogen is contained in the polynuclear cells
as a rule; nevertheless in certain diseases cells are always found which
give a marked iodine reaction. In this manner the appearance of cells
containing glycogen in diabetes was first proved. (Ehrlich,
Gabritschewsky, Livierato.) The iodine reaction in the white blood
corpuscles is also seen in severe contusions and fractures, in
pneumonias, in rapidly progressing phlegmata from streptococcus and
staphylococcus, after protracted narcosis (Goldberger and Weiss).
Ehrlich explains the appearance of glycogen as follows. The glycogen is
not present in the cell as such, but in the form of a compound, which
does not stain with iodine. This compound readily splits off glycogen,
which then gives the iodine reaction[12].
We cannot regard the perinuclear green granules, described by Neusser in
the polynuclear cells, as pre-existing. (See p. 42.)
The number of polynuclear leucocytes in the blood of the healthy adult
amounts to about 70-72%, of the total white corpuscles. (Einhorn.)[13]
5. =The eosinophil cells.= These are characterised by a coarse, round
granulation, staining deeply with acid dyes, and similar in other
respects to the polynuclear neutrophils. With faint staining, a thin
peripheral layer of the eosinophil granule is seen more deeply stained
than the interior. The nucleus as a rule is not so deeply stained as in
the polynuclear neutrophil, but otherwise in its general shape is
completely similar. Both forms have in common a considerable
contractility, which renders possible their emigration from the vessels,
and their appearance in exudations and in pus. The size of the
eosinophils frequently exceeds that of the neutrophils. Their number is
normally about 2-4% of the white cells.
6. The mast cells. These are present, though very sparingly, in every
normal blood; 0.5% is their maximum number in health.
Their intensely basophil granulation, of very irregular size and unequal
distribution, must specially be mentioned. The granulation possesses the
further peculiarity, in that with the majority of basic dyes it stains,
not in the pure colour of the dye, but metachromatically--most deeply
with thionin. As Dr Morgenroth found, the deviation from the colour of
the dye is still more marked with Kresyl-violet-R (Muelheim manufactory),
when the granules stain almost a pure brown.
The staining power of the nuclei is very small, and it is therefore hard
to make out the shape of the nucleus without the use of difficult
methods. In triacid preparations the granulation is unstained, and the
mast cells appear as clear, polynuclear cells, free from granules.
* * * * *
So much for the colourless cells in the blood of the normal adult.
In pathological cases, not only do the forms so far mentioned occur in
altered numbers, but abnormal cells also make their appearance. To these
belong:
1. =Mononuclear cells with neutrophil granulation.= ("=Myelocytes=,"
Ehrlich.) Generally they are bulky, with a relatively large, faintly
staining nucleus, often fairly centrally placed, and equally surrounded
by protoplasm on all sides. A fundamental distinction from the large
mononuclear cells lies in the fact that the protoplasm exhibits a more
or less numerous neutrophil granulation. Besides the larger myelocytes,
much smaller forms, approximating to the size of the erythrocytes are
also found. All transitions between these two stages are likewise met
with. In contradistinction to the polynuclear neutrophil elements, these
mononuclear forms shew no amoeboid movement on the warm stage. They
form a constant characteristic of myelogenic leukaemia, and in these
cases generally occur in large numbers.
Reinbach has found them in a case of lymphosarcoma with metastases in
the bone-marrow. A. Lazarus observed their transitory occurrence in
moderate number in a severe posthaemorrhagic anaemia. M. Beck observed
them in the blood of a patient with severe mercury poisoning. They are
also frequently found in children's diseases, especially in _anaemia
pseudoleukaemica infantum_. K. Elze established their presence in a boy
of 15 months, suffering from a slowly progressing tuberculosis of the
lymphatic glands.
The appearance of myelocytes in infectious diseases is particularly
interesting. Rieder had previously demonstrated that myelocytes may be
present in acute inflammatory leucocytoses; and recently a thorough
work by C. S. Engel has appeared upon the occurrence of myelocytes in
diphtheria. Engel discovered the interesting fact, that myelocytes are
often to be found in children suffering from diphtheria, and further
made the important observation that a high percentage of myelocytes
(3.6-16.4% of the white elements) only occurs in severe cases, and
points to an unfavourable prognosis. Myelocytes are also present in mild
cases, though not constantly and in much smaller number. Tuerk has
recently undertaken a very exact and thorough analysis of their
occurrence in infectious diseases, in the course of which he accurately
tabulated the white corpuscles in a large number of cases. The results
he obtained in pneumonia are especially characteristic, for he found at
the commencement of the disease that myelocytes are not seen at all or
only very scantily: and it is only at the time of the crisis, or
directly afterwards, that they become specially numerous. In isolated
cases the increase at this time was very considerable; and in one case
amounted almost to 12% of all neutrophil cells.
2. Mononuclear eosinophil cells ("=eosinophil myelocytes="). H. F. Mueller
was the first to point out their importance. They constitute the
eosinophil analogue of the previous group, and are much larger than the
polynuclear eosinophils; medium and small sized examples are often found
in leukaemia. Eosinophil myelocytes are almost constantly present in
myelogenous leukaemia and in anaemia pseudolymphatica infantum. Apart from
these two diseases they are very rarely found; Mendel saw them for
example in a case of myxoedema, Tuerk quite exceptionally in some
infectious diseases.
3. =Small neutrophil pseudolymphocytes.= They are about as large as the
small lymphocytes, possess a rounded deeply stained nucleus, and a small
shell of protoplasm studded with a neutrophil granulation. The
relatively deep stain of the nucleus and the small share of the
protoplasm in the total cell body prevent confusion with the small forms
of myelocytes, which never reach such small dimensions. The neutrophil
pseudolymphocytes are exceedingly infrequent, and represent products of
division of the polynuclear cells; they were first described by Ehrlich
in a case of hemorrhagic small-pox. The process of division goes on in
the blood in such a manner that the nuclear rod first divides into two
to four single nuclei, and then the whole cell splits up into as many
fragments. These cells occur also in fresh pleuritic exudations. After a
time the nucleus of these cells becomes free, and the little masses of
protoplasm thus cut off are taken up mostly by the spleen substance. The
free nucleus likewise shares in the destruction. It is of the greatest
importance that these cells, which up to the present have not elsewhere
been described, should receive more attention. They must be of
significance, in particular for the question of transitory
hyperleucocytosis, which is by some referred to a destruction, by others
to an altered localisation of the white blood corpuscles.
4. "=Stimulation forms=" were first described by Tuerk, and are mononuclear
non-granulated cells. They possess a protoplasm staining with various
degrees of intensity, but in any case giving with triacid solution an
extraordinarily deep dark-brown, and further a round simple nucleus
often eccentrically situated, stained a moderately deep bluish-green,
with however a distinct chromatin network. The smallest forms stand
between the lymphocytes and the large mononuclear leucocytes, but
approach the first named as a whole in their size and general
appearance. According to Tuerk's investigations, these cells often occur
simultaneously with, and under the same conditions as the myelocytes.
Their importance cannot at present be accurately gauged. Possibly they
form an early stage of development of the nucleated red blood
corpuscles, as the deeply staining and homogeneous protoplasm seems to
indicate.
With the description of these abnormal forms of white corpuscles all
occurring forms are by no means exhausted. We are here excepting
completely the variations in size which particularly affect the
polynuclear and eosinophil cells, and which lead to dwarf and giant
forms of them. For however considerable the difference in size, these
cells always possess characteristics sufficient for an exact diagnosis.
But besides these, isolated cells of an especially large kind are found
particularly in leukaemic blood, and concerning their importance and
relationship we are up to the present in the dark.
FOOTNOTES:
[11] In enumerating the blood corpuscles, 2 and 3 may be counted
separately or in one group.
[12] The assumption of Czerny, that the cells which react to iodine
emigrate from suppurating foci, is without foundation. A simple
investigation of freshly inflamed tissue is sufficient to show that the
cells which have wandered from the blood stream soon contain glycogen.
[13] Kanthack described this group as "finely granular oxyphil" cells.
Their granules stain red in eosine and in eosine-methylene blue
solutions, but the colour is different from that of the true eosinophil
cells, and much less intense. In the latter mixture they stain really
with the methylene blue salt of eosine. Their true nature is shown by
their behaviour with the triacid solution.
II. ON THE PLACES OF ORIGIN OF THE WHITE BLOOD CORPUSCLES.
For the comprehension of the histology of the blood as a whole, it is of
great importance to obtain an exact knowledge how and to what extent the
three organs, which are undoubtedly very closely connected with the
blood, lymphatic glands, bone-marrow, and spleen, contribute to its
formation. The most direct way of deciding the question experimentally
by excision of the organs in question, is unfortunately only available
for the spleen. The part played by the lymphatic glands and bone-marrow,
whose exclusion _in toto_ is not possible, must mainly be determined by
anatomical and clinical considerations. But only by a careful
combination of experiments on animals, of anatomical investigations, and
especially, of clinical observations on a large scale, can light be
thrown on these very difficult questions. It cannot be emphasised
sufficiently how important it is that everyone engaging in haematological
work should first of all collect a large series of general observations;
otherwise errors are bound to occur. For instance, the endeavour is
often made to compensate the lack of personal experience by careful
literary studies; but in this way the histology of the blood falls into
a vicious circle, of which the new phase of blood histology affords
many examples. And it is characteristic of this kind of work that from
the investigation of a single rare case, most far-reaching conclusions
on the general pathology of the blood are at once drawn; _e.g._ Troje's
paper, in which having failed to recognise the lymphocytic character of
a case of leukaemia, and believing therefore that he had to do with a
myelogenous leukaemia, the author denied and completely reversed all that
had been previously established about this disease. It is equally hard
to avoid errors if one confines oneself exclusively to animal
experiments, without supplementing these by clinical experience, as is
shewn by the numerous papers of Uskoff. Not the anatomist, not the
physiologist, but only the clinician is in the position to discuss these
problems.
In the introduction to this chapter we have already alluded to the
striking retrograde movement in haematology at the present time, brought
about by the view that the white corpuscles as a whole are derived from
the lymphocytes. If we disregard the embryological investigations on
this point (Saxer), anatomists, physiologists, and clinicians alike have
taken up a similar point of view. Among anatomical papers we may refer
to those of Gulland, according to whom all varieties of leucocytes are
but different stages of development of one and the same element. He
distinguishes hyaline, acidophil and basophil cells, and derives all
from the lymphocytes. Arnold advocates similar views, though in a
negative form. He says that a distinction between so-called lymphocytes
and the leucocytes with polymorphous nuclei, on the grounds of the form
of the cell and nature of the nucleus, is not possible at the present
time. Neither is a classification based on the granules admissible,
since the same granules occur in different cells, and different
granules in the same cell. The work of Gulland and Arnold takes into
consideration the differential staining of the granules in various ways.
In spite of their facts we disagree with their conclusions; and we shall
therefore have to analyse them in the special description of the
granulated cells and granules.
Recently (since 1889) Uskoff has in particular published experimental
work in this province of haematology. This has led him to see in the
white blood corpuscles the developmental series of one kind of cell, and
to distinguish in it, three stages: (1) "young cells," which correspond
to our lymphocytes; (2) "ripe cells" (globules murs), large cells with
fairly large and irregularly shaped nucleus, which are therefore our
large mononuclear and transitional forms; (3) "old cells" (globules
vieux), which represent our polynuclear cells. The eosinophil cells are
completely excluded from this classification. Amongst clinicians A.
Fraenkel has recently gone in the same direction, and on the grounds of
his experience in acute leukaemias has supported the view of Uskoff, that
the lymphocytes are to be regarded as young cells, and early stages of
the other leucocytes. But few authors (for instance C. S. Engel,
Ribbert) have raised a protest to this mixing of all cell forms of the
blood, and have held to the old classification of Ehrlich. But as it is
emphatically taught in numerous medical works that all these cells are
closely related, the grounds for sharply separating the lymphocytes from
the bone-marrow group may here be shortly summarised, and stress laid on
the great importance which this apparently purely theoretical question
has for clinical observation. We shall come to most important
conclusions upon this point when we consider more closely the share
which the various regions of the haematopoietic system take in the
formation of the blood, and especially of the colourless elements.
[alpha]. The Spleen.
The question whether the ~spleen~ produces white blood corpuscles has
played a large part from the earliest times of haematology.