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.

Nevertheless, a considerable time elapsed before the powerful impulse 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.



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.



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.

Endeavours were first made to investigate the participation of the spleen in the formation of the white blood corpuscles by counting the white corpuscles in the afferent and efferent vessels of the spleen. It was thought that the blood-forming power of the spleen was proved by the larger number of corpuscles in the vein as compared with the artery. The results of these enumerations however are very varying; the investigators who found a relative increase in the vein are opposed by other investigators equally reliable; and with the experience of the present day one would not lay any value on these experiments.

We must emphasise the fact, established by later researches, that after extirpation of the spleen, an enlargement of various lymphatic glands occurs. The alterations of the thyroid, which have been observed by many authors, cannot be described as constant.

Further, the blood investigations which Mosler, Robin, Winogradow, Zersas and others have carried on in animals and man after removal of the spleen must here be mentioned. These have already proved that a leucocytosis occurs after some considerable time. Prof. Kurloff carried out detailed investigations in 1888 in Ehrlich's laboratory, and carefully studied the condition of the blood after extirpation of the spleen. As the work of Prof. Kurloff has so far only appeared in Russian, his important results may be here recorded more fully. For his researches, Kurloff employed the guinea-pig, as this animal by its peculiar blood is specially suited for this purpose.

In order to give a systematic account of the results of these important investigations, we must first shortly sketch the normal histology of the blood of the guinea-pig according to Kurloff.

In the blood of the healthy guinea-pig the following elements are found.

I. Cells bearing granules.

1. Polynuclear, with pseudoeosinophil granulation. This granulation, which Ehrlich had previously found in the rabbit, is easily distinguishable from the true eosinophil, since it is much finer, and stains quite differently in eosine-aurantia-nigrosin mixtures. One principal distinction between these two forms of cells lies in the fact that, according to Kurloff, this granulation is very easily dissolved by acid, but remains unchanged in alkaline solutions; doubtless an indication that the granulation consists of a basic body soluble with difficulty, which with acids forms soluble salts. The true eosinophil granulation remains, on the other hand, quite unchanged under these conditions.

These pseudoeosinophil, polynuclear cells, correspond functionally to the neutrophil polynuclear of man; their number amounts to 40-50% of the total white cells. The red bone-marrow is to be regarded as the place of origin of this kind of cell. It contains very many pseudoeosinophil cells, and indeed all stages are to be found in it, from the mononuclear cells bearing granules to the fully formed polynuclear.

2. The typical eosinophil leucocytes, which fully correspond to those found in man, and amount to about 10% of the number of the white.

3. The "nigrosinophil cells," as they are called by Kurloff. In their general appearance, in the size of the cell and the granulation, they completely correspond to the eosinophil cell. The only distinction between them consists in a chemical difference in the granulation. These cells stain in the colour of nigrosin in the aurantia-eosin-nigrosin mixture, whilst the eosinophil cells become red. The two granulations always show different shades in the triacid preparation as well; for the nigrosinophil cells stain a blacker hue.

II. Cells free from granules.

([alpha]) Cells with vacuoles.

This is a quite peculiar group, characteristic for the blood of the guinea-pig. It shews transitions in the blood, from large mononuclear to transitional and polynuclear forms, but is marked by the lack of any kind of granulation. Instead of the latter, we find in these cells a roundish, nucleus-like form in the protoplasm, which also takes the nuclear stains, and possibly is to be considered an accessory nucleus. We have received the impression that we have here to deal with a vacuole filled with substance secreted by the cell. In a large series of preparations, it is possible to obtain some elucidation of the development and fate of these appearances. They first appear as point-like granules in the protoplasm, bearing no relation to the cell nucleus; they gradually increase, and acquire a considerable circumference. When they have attained about the size of the cell nucleus, they, or rather their contents, appear to break through the protoplasmic membrane and to leave the cell.

The number of the vacuole containing cells is 15-20% of the colourless blood corpuscles.

([beta]) Typical lymphocytes.

Their appearance completely corresponds with that of human lymphocytes as described above. They make up 30-35% of the total number of leucocytes.

Now Kurloff in the course of extremely careful and laborious researches, estimated the total number of leucocytes, and then from the percentage numbers, the total quantity of pseudoeosinophil, neutrophil, eosinophil, vacuole containing cells, and lymphocytes, and could thus demonstrate that in uncomplicated cases of removal of the spleen, where inflammatory processes, accompanied by an increase of the polynuclear neutrophil corpuscles, were avoided, a gradual increase of the lymphocytes alone in course of time results. This may be a two- or threefold increase, whereas the numbers of all other elements remain unchanged.

Kurloff obtained his figures as follows: first he estimated the relative proportion of the different kinds of white blood corpuscles one to another in a large number of cells (500 to 1000). A count of this kind however gives no evidence as to whether one or other kind of cell is absolutely increased or diminished. A fall in the percentage of the lymph cells may be brought about by two quite different factors: (1) by a diminished production of lymphocytes, (2) by an increased influx of polynuclear forms, which naturally lowers the relative count of the lymphocytes. It was therefore necessary to obtain a method which would show alterations in the absolute number of the individual forms of leucocytes. Kurloff used for this purpose the "comparative field"; that is, he counted by the aid of a moveable stage the different forms which lay on a definite area (22 sq. mm.) of the dried blood preparation. This procedure gave very exact results, as only faultlessly prepared, and regularly spread preparations were used. The following figures (from Exp. II.) illustrate the method and its results:

April 12 52% pseudo-eos. 10% lymphocytes counted. Sept. 2 (one month after the operation) 22% " 53% " "

By the aid of the comparative surface, these figures were supplemented by the following averages. On each surface used for comparison were found:

April 12 38 white = 19.8 pseudo-eos. 10.6 lymphocytes. Sept. 2 81 " 18.0 " 46.9 "

From this example it follows without doubt, that the total number of the white blood corpuscles had about doubled itself, but that in this increase the lymphocytes exclusively were concerned, and the pseudo-eosinophil cells had not undergone the smallest increase.

The results which Kurloff obtained by means of this method in animals whose spleens had been removed, may be illustrated by one of his original researches and its accompanying chart and table.

Exp. I. Young female, weight 234 gr. Number of red corpuscles in a cubic millimeter of blood 5,780,000. Number of white 10,700. On April 19, 1888, the spleen was removed, the wound healed by first intention. The results of the further investigation of the blood are found in the following table.

From the chart and table, the number on the surface of comparison of the white blood corpuscles is seen to have more than doubled itself in the first seven months, and that this increase was solely dependent on the flooding of the blood by lymphocytes. The nucleated or bone-marrow elements and the large mononuclear cells remained continuously at the same level during the whole period. The changes in the percentage proportions ran somewhat differently. The percentages rose from 35 to 66% for the lymphocytes only, whilst for the other forms they distinctly fell: for the nucleated from 44% to 22% and for the large mononuclear from 18% to 9%. It was only in the course of the second year that a very considerable relative and absolute increase of the eosinophil cells appeared: the values rose gradually from about 1.0% to 28.9% or from 0.5 to 13.9 on each comparison area. The last examination of the blood in this animal was made on April 30, 1890, that is, two years after the removal of the spleen. The animal was quite healthy, bore four healthy young guinea-pigs by a father whose spleen had been removed. The young have a completely normal spleen, and their blood likewise shows no abnormalities.



TABLE I.

Key to columns: A - Leucocytes B - Pseudo-eosinophil cells C - Lymphocytes D - Large mononuclear cells E - Eosinophil cells F - Nigrosinopil cells G - On comparative surfaces

- A B C D E F Date Total G % G % G % G % G % G - 1888 April 19 500 44.7 35.4 18.4 1.1 0.5 23 990 24 40.4 9.7 35.6 8.5 21.6 5.2 1.9 0.4 0.4 0.09 May 1 858 28 47.0 13.6 32.6 9.1 18.0 5.0 0.9 0.2 0.3 0.08 8 934 28 45.2 12.6 40.3 11.3 14.3 4.0 0.6 0.2 0.4 0.1 16 1122 30 38.4 11.5 47.7 14.3 10.3 3.1 3.3 0.9 0.2 0.06 24 1722 35 40.1 14.0 35.0 12.2 23.6 8.3 1.0 0.3 0.1 0.03 30 900 30 36.6 10.9 44.4 13.3 18.4 5.5 0.1 0.03 0.3 0.09 June 5 825 33 28.4 9.4 49.3 16.2 20.0 6.6 1.7 0.6 0.4 0.1 12 1314 33 28.0 9.3 49.0 16.2 20.0 6.6 2.2 0.7 0.8 0.3 19 917 37 32.4 11.9 52.3 19.3 14.5 5.4 0.6 0.3 0.2 0.07 28 802 42 30.5 12.8 56.4 23.7 11.7 4.9 0.7 0.3 0.4 0.2 July 2 1062 56 16.5 9.2 57.1 31.9 25.6 10.3 1.2 0.7 1.2 0.7 9 1245 51 17.6 8.9 59.1 30.1 21.8 11.1 0.8 0.4 0.8 0.4 16 974 69 17.5 12.0 66.4 45.8 15.7 10.8 0.2 0.1 0.2 0.1 23 1156 58 21.7 12.6 67.2 38.9 9.5 5.5 1.5 0.9 0.2 0.1 30 802 54 20.2 10.7 65.4 34.6 12.8 6.8 1.4 0.7 Aug. 6 910 52 21.7 11.3 67.3 34.9 9.7 4.9 1.0 0.5 0.3 0.2 Sept. 6 815 51 23.0 11.7 65.3 33.5 9.8 4.9 0.9 0.5 0.4 0.2 Oct. 5 625 62 26.4 16.3 64.4 39.9 8.5 5.2 0.6 0.4 Nov. 4 800 58 22.5 13.0 66.4 38.5 9.6 7.3 0.9 0.5 0.5 0.2 1889 April 10 700 29.8 53.3 14.8 1.2 0.6 June 6 900 71 28.2 20.0 50.1 35.6 12.9 9.1 8.2 5.8 0.6 0.4 Aug. 1 670 62 30.6 18.9 44.2 27.4 15.2 9.4 9.6 5.9 0.4 0.2 Dec. 4 731 63 36.0 22.0 38.3 24.1 11.3 7.1 13.3 8.7 0.6 0.4 1890 Feb. 2 622 51 32.3 16.5 30.1 15.3 11.1 5.6 26.0 13.2 0.5 0.2 April 30 500 48 36.5 17.5 24.5 11.7 9.4 4.5 28.9 13.9 0.6 0.3 -

The results of further investigations, which we here shortly repeat in tabular form, shew that in this experiment No. I. we are not dealing with an abnormal phenomenon of an exceptional animal.

Number of white blood corpuscles No. of - Expt. Before the At the end of At the end of splenectomy the first year the second year 1 10,700 14,200 18,000 2 12,000 27,600 32,000 4 15,000 19,200 19,000 Average 12,600 20,333 23,300

By estimating the percentage proportion of the single kinds of white corpuscles, Kurloff obtained the following result:

Key: A - Number of the Experiment B - Polynuclear granular cells C - Lymphocytes D - Mononuclear E - Eosinophil

Before the operation At the end of the At the end of the first year second year A B C D E B C D E B C D E 1 4782 3788 1969 117 4232 1568 2101 170 6570 4410 1692 5202 2 6276 3360 2244 72 5464 16615 2980 2539 5824 20861 2688 2240 4 6715 5250 2595 450 6568 10041 3686 96 7108 3009 2138 7543

From these researches we draw the following conclusions.

1. The spleen is not an indispensable, vitally important organ for the guinea-pig, since that animal bears splenectomy without loss of health, developes normally, and gains well in weight.

2. The hypertrophy and hyperplasia of the lymph glands, particularly of the mesenteric glands, which develop after the operation correspond to a lymphocytosis, which makes its appearance in the course of the first year after the operation so constantly that it may be looked upon as a characteristic sign of the absence of the spleen. This increase may amount to double and more. We must therefore assume that the deficiency of splenic function may be met by the lymphatic glandular system. This period of lymphaemia may doubtless in some animals persist for years in exceptional cases; in the majority, however, the lymphaemia diminishes in the course of the first year, and indeed subnormal quantities of lymphocytes may then be produced.

3. The cells of the bone-marrow, on the contrary, and the polynuclear pseudoeosinophil cells do not show the least variation in the course of the first year. Bearing in mind that under normal conditions these cells are met with exclusively in the bone-marrow, and that inflammation in animals after removal of the spleen is accompanied by an acute pseudoeosinophil leucocytosis, exactly as in normal animals, one must admit that the production and function of this kind of cell are quite independent of the spleen. Hence there can be no doubt about their myelogenic nature.

4. It is especially important that the mononuclear and the leucocytes associated with them, undergo no increase. As these cells under normal circumstances occur both in the spleen and in the bone-marrow, we must assume that normally also the bone-marrow is responsible for the majority of this kind in the blood, and that the deficiency in the splenic contribution can be easily covered by a slightly raised activity of the bone-marrow. Were the share of the spleen important, from general biological considerations, an over-production of the kind of cell in question must occur in the vicarious organs.

5. The increase of the eosinophil cells, which constantly makes its appearance in the second year after the operation, is highly interesting, and leads to a really enormous rise in their absolute and relative numbers. Their percentage number once rose to 34.6%, and their absolute quantity amounted at the end of the second year on the average to 30-50-fold their original number (see table).

Hence it follows from Kurloff's researches that the spleen of the guinea-pig plays quite an unimportant part in the formation of the white blood corpuscles, and that after splenectomy in the first year compensation occurs only in the lymph-glands, followed in the second year by a great increase of the eosinophil cells. It is to be particularly insisted once again that the spleen has nothing at all to do with the formation of the pseudoeosinophil polynuclear cells, which are the analogues of the polynuclear neutrophils of man.

* * * * *

How do observations on man stand in the light of Kurloff's observations, which might be regarded as depending on peculiarities of the particular kind of animal?

Completely analogous material is afforded by cases, in which in healthy people a splenectomy has been necessary in consequence of trauma. Unfortunately the material available for this purpose is extremely rare; and it would be of the utmost value if the alterations of the blood in such a case were systematically studied for a period of years. We have ourselves begun our observations in two patients directly after the operation, but were unable to continue them, as death occurred within the first week after the extirpation. Up to the present only seven cases of rupture of the spleen with subsequent splenectomy have been published, as is stated in the collection of cases of v. Beck. In two only, of these seven cases, one of Riequer's (Breslau) the other of v. Beck's (Karlsruhe) was a cure effected. Through the courtesy of the above-mentioned gentlemen, we were able to investigate specimens from these two patients.

In the case of v. Beck the operation was performed on June 15, 1897. We received a dry blood preparation about 6 months after operation. Investigation showed a considerable lymphaemia: the bulk of the lymphocytes belonged to the larger kinds: the eosinophil cells were certainly not increased. For other reasons an exact numerical analysis could not be undertaken. We hope to be able to follow the further course of this case.

In the second case the operation was performed on May 17, 1892, by Dr Riequer of Breslau, for trauma, and later described. We made counts in oldish and fresh preparations. It is worthy of notice that this case is not uncomplicated, as an amputation of the thigh was performed shortly after the splenectomy on account of gangrene.

We found the following figures.

Preparations from Polynuclear Lymphocytes Eosinophil Large mononuclear June 12, 1892 81.9% 15.9% 1.3% October 11, 1892 80.0% 13.7% 4.0% 1.7% September, 1897 56.8% 33.1% 3.5% 1.5%

It is much to be regretted that dry preparations only at the beginning and at the end of the five year period of observation were at our disposal. It appears from the paper of Riequer as if in this case the lymphocytosis had established itself one month after the operation, and had lasted for a very long time, just as Kurloff has found in some animal experiments. Just as little as a polynuclear increase is abnormal, is an increase of the lymphocytes remarkable; and in this case the lymphocytic increase was recognisable after the end of the fifth year. The eosinophil cells oscillate at this period about the upper normal limit. From all that we know, it is probable that their number in the meantime had undergone an intercurrent increase.

The cases are more frequent in which a splenectomy has been undertaken on account of disease of the spleen. Amongst these, the clearest results are a priori to be expected from splenic cysts, since the part of the spleen not affected by the cyst formation often shews quite a normal structure, and therefore is physiologically active. On the other hand, the excision of chronic splenic tumours may be—for the blood condition—of no importance inasmuch as the function of the spleen may have previously long been eliminated by pathological changes.

Amongst these cases, we must in the first place mention the well-known and carefully investigated case of B. Crede. In a man 44 years of age the spleen was extirpated on account of a large splenic cyst. Within two months of the operation there developed a thoroughly leukaemic condition of the blood, exclusively brought about by the increase of the lymphocytes, as is seen from the results of Crede and the table contained in his paper. It is further remarkable that four weeks after the operation a painful doughy swelling of the whole thyroid appeared, which remained, with variations, for nearly four months. With the general recovery of the patient this shrank to a small remnant. We notice further that this very interesting swelling of the thyroid, which doubtless stands in the closest connection with the splenectomy, is nevertheless no constant accompaniment of this operation, as for instance in the case of v. Beck, where it was not present.

The most recent work on extirpation of the spleen for tumours is from Hartmann and Vasquez. As the result of their researches the authors arrive at the following conclusions:

1. A slight post-operative increase of the red blood corpuscles and a true acute hyperleucocytosis occur and pass rapidly away.

2. The haemoglobin equivalent of the corpuscles sinks at first but recovers its original value by degrees.

3. 4-8 weeks afterwards a lymphocytosis of varying duration is established.

4. Later, after many months, a moderate eosinophilia occurs.

We have ourselves been able to investigate three conclusive cases.

The first was a patient, which we were ourselves enabled to investigate by the courtesy of Dr A. Neumann. The patient's spleen was removed by E. Hahn on account of an echinococcus on Feb. 5, 1895. One may well assume that before the operation the spleen no longer discharged its normal function. On Sept. 2, 1897, we found the following numerical proportions:

Polynuclear neutrophil 76.5%, Lymphocytes 18.4%, Eosinophil 3.4%, Large mononuclear 1.1%, Mast cells 0.4%.

A condition therefore which was quite normal. In this connection it must be mentioned that an incipient phthisis pulmonum existed at the time, to which we must attribute an increase of the polynuclear elements, and without which the percentage figures of the lymphocytes and eosinophils would perhaps have been greater.

For the knowledge of the two other cases we are indebted to the kindness of Professor Jounescu of Bucharest. The one case was of a man of about 40 years of age, in whom splenectomy was undertaken on Sept. 27, 1897, for an enlarged spleen. Healing by first intention. The white blood corpuscles were permanently increased. The proportion of white to red was 1:120 to 1:130, the average number of red was 3,000,000. Our own examination of preparations obtained some two months after the operation, shewed a distinct lymphaemia, and also a preponderance of the larger lymph cells. The eosinophil and mast cells were plainly increased. We are unable to give more exact numerical data, as the preparations sent to us were not spread with sufficient regularity.

From the second case, which was also operated upon for enlargement of the spleen, we unfortunately only obtained much damaged preparations. Nevertheless so much could with certainty be established—that there was no considerable increase of the lymphocytes. The eosinophils on the contrary were increased distinctly, the mast cells to a lesser extent. It is probable that the increase of both of the latter kinds of cell was not a consequence of the extirpation of the spleen alone, but rather the expression of the reactive changes, which had already begun before the operation, from the exclusion of the splenic function.

Cases of splenectomy of this kind are transitional to the chronic diseases of the spleen. The latter present great difficulties, for one never knows how far in the most chronic diseases the other organs are damaged or influenced by the general illness.

An increase of the lymphocytes, so long as an affection of the lymphatic glands may be excluded, should be referred to functional exclusion of the spleen.

On the other hand, an increase of eosinophil cells associated with a chronic tumour of the spleen, is analogous to Kurloff's secondary reaction of the bone-marrow. Such cases are frequently found in the literature. For instance Mueller and Rieder bring forward three cases of splenic tumour caused by congenital syphilis, cirrhosis of the liver, neoplasm in the cranial cavity, and in which the numbers of the eosinophils amounted to 12.3%, 7.0%, 6.5% respectively. In three cases of acute splenic tumour in typhoid fever the figure 0.31% with a maximum of 0.82%, was found. These authors have already raised the question "whether the increase of the eosinophil cells is connected with the splenic tumour or the bone-marrow? Perhaps the functional activity of the latter is vicariously raised to meet the more or less complete exclusion of the spleen from the formation of the blood; since Ehrlich has distinctly asserted that the probable place of formation of the eosinophil cells is the bone-marrow."

From what has been brought forward no doubt can now remain that the question has been decided quite in Ehrlich's favour.

But what then are the physiological functions of the spleen, since that organ is unnecessary for the persistence of life? Doubtless its chief duty is the taking up of the greater part of the decaying fragments of red and white blood corpuscles in the blood-stream, so that this valuable material is not quite lost for the organism. Thus Ponfick has found that after destruction of the red corpuscles the spleen takes up a portion of their "shadows," and for this reason calls the splenic tumour a spodogenous splenic tumour ([Greek: spodos], ruins). Ehrlich has made a corresponding observation for the products of dissolution of the white blood corpuscles, and has proved that the splenic tumour which occurs in many infectious diseases and in phosphorus poisoning is to a large extent caused by the parenchyma of the spleen taking up the remains of the neutrophil protoplasm.

The question of the relation of the spleen to the fresh formation of red blood corpuscles is a problem of comparative anatomy. Observations on this point made on one kind of animal can certainly not claim validity for other kinds. In lower vertebrates, as in fishes, frogs, tortoises, and also in birds, the blood-forming activity of the spleen is pronounced and of great importance. In mammalia on the other hand, in some cases this function cannot be demonstrated, and in others only to a very small degree. In the spleen of normal mice nucleated red blood corpuscles are seen in relatively large numbers; in the rabbit they are less numerous and often only to be found with difficulty. In the dog they only make their appearance after anaemia from loss of blood, normally they are absent. In the human spleen nucleated red blood corpuscles are not to be found normally or in cases of severe anaemia, but exclusively in leukaemic diseases. U. Gabbi in his recently published work on the haemolytic function of the spleen, also emphasises the difference between the various animal species. In guinea-pigs he found that the spleen acts largely as a scavenger of the red blood corpuscles; in rabbits very slightly. Consequently after removal of the spleen in guinea-pigs the number of red blood corpuscles rose 377,000 in the cubic millimetre, and the amount of haemoglobin 8.2%. After splenectomy in rabbits the increase in these values is absent.

Shortly summarising our analysis of the facts before us, we must say that the importance of the spleen for the production of the white blood corpuscles can in no respect be considerable, and that if these cells really are produced by it, they must be free from granulations. The spleen therefore stands functionally in closer connection with the lymphatic gland system than with the bone-marrow. The spleen has not the least connection with ordinary leucocytosis[14].

([beta]) The Lymphatic Glands.

As it is impossible experimentally to prevent the lymphatic glands as a whole from contributing to the formation of the blood, we are dependent almost entirely on clinical and anatomical researches for an elucidation of their function.

Since Virchow's definition of the lymphocyte it has been admitted that the lymphocytes of the blood, both the small and larger kinds, are identical with those of the lymphatic glands and the rest of the lymphatic system. This is proved by the complete agreement in general morphological character, in staining properties of the protoplasm and nucleus, and from the absence of granulation.

Abundant clinical experience testifies that the lymphocytes of the blood really do arise from the lymphatic system. Ehrlich had previously observed that when extensive portions of the lymphatic glandular system are put out of action by new growths and similar causes, the number of the lymphocytes may be considerably diminished. These observations have since that time been confirmed by various authors. For example, Reinbach describes several cases of malignant tumour, particularly sarcoma, in which the percentage of lymphocytes, which normally amounts to about 25%, was very considerably lowered; in one case of lymphosarcoma of the neck they only made up 0.6% of the total number. These conditions are quite easily and naturally explained by the exclusion of the lymphatic glands. It is difficult for the advocates of the view that the lymphocytes are the early stages of all white blood corpuscles to reconcile it with these facts. According to their scheme the low number of lymphocytes is to be explained in such cases by their unusually rapid transformation to the polynuclear elements—the old forms; or to appropriate the expression of Uskoff, by a too rapid ageing of the lymphocytes.

Further evidence for the origin of the lymphocytes of the blood from the lymphatic glands is to be obtained from those cases in which we find an increase of the lymphocytes in the blood. These "lymphocytoses" occur, in comparison with other leucocytoses, relatively seldom. Under certain conditions in which a hyperplasia of the lymphatic glandular apparatus makes its appearance, we often see at first an increase of the lymphocytes in the blood. Ehrlich and Karewski in some unpublished work have investigated together a large number of typical cases of lymphoma malignum, and were able constantly to observe a lymphocytosis, which in some cases was of high degree and bore almost a leukaemic character.

Relying on these facts Ehrlich and Wassermann (Dermatolog. Zeitschr. Vol. I., 1894) made the diagnosis in vivo of malignant lymphoma in a rare skin disease, chiefly from the absolute increase of the lymphocytes alone, although no swelling of the glands was palpable. The post-mortem shewed that the chief condition was a swelling of the retro-peritoneal lymph glands to lumps as large as a fist.

The lymphocytosis following extirpation of the spleen also belongs to this category, since a vicarious enlargement of the lymph glands is always to be observed in these cases.

On investigating the conditions under which in healthy individuals an increased number of lymphocytes enter the blood-stream, we have in the first place to notice the digestive canal, whose wall contains a thick layer of lymphatic tissue. According to the results of Rieder the proportion of the lymphocytes to polynuclears is practically normal in the leucocytosis of digestion, indeed the lymphocytes are rather in excess. The eosinophils on the other hand shew a marked relative reduction in this condition. The leucocytosis of digestion consequently differs essentially from the other kinds, in which the neutrophil elements are chiefly increased. The simultaneous increase of lymphocytes and polynuclears is doubtless brought about by a super-position of a raised income of lymphocytes, and an ordinary leucocytosis caused by the assimilated products of metabolism.

The influence of the digestive tract is still more evident in certain diseases, more particularly in intestinal diseases of infants. A considerable increase of the lymphocytes in the blood-stream is here to be observed. Thus Weiss found an important increase of the white blood corpuscles in simple catarrh of the stomach and intestines, which presented the main features of a lymphocytosis.

Whooping-cough, according to the recent observations of Meunier, also belongs to the small number of diseases which are accompanied by a pronounced lymphaemia. In the convulsive period of this disease both the polynuclear cells and the lymphocytes are increased, the latter in preponderating amount. The former cells are increased to twice, the lymph cells to four times their normal amount. Doubtless in these cases also the lymphocytosis is due to the stimulation and swelling of the tracheobronchial glands.

An increase of the lymphocytes from chemical stimuli is exceedingly rare, though, as is well known, a large number of substances (bacterial products, proteins, nucleins, organic extracts, and so forth) can call forth a polynuclear leucocytosis. In quite isolated cases, an increase of the lymphocytes in the blood in consequence of the injection of tuberculin into tuberculous individuals has been seen. (E. Grawitz.) From the rarity of these cases it can scarcely be doubted that here a tuberculous disease of the glands also plays a part, so that the increased immigration of lymphocytes is brought about not by a chemical property of the tuberculin but by the extensive specific reaction of the diseased glands.

Only one single substance has so far been mentioned in the literature as capable in itself of producing a lymphocytosis. Waldstein asserts that he has produced by injection of pilocarpine, a lymphaemia which undergoes a progressive increase with a rise in number of the injections.

The origin also of lymphocytosis is therefore sharply marked off from that of the ordinary leucocytosis, which consists in an increase of the neutrophil elements. Whilst the latter is admittedly the expression of chemiotactic action, and arises by action at a distance of soluble substances on the bone-marrow, lymphocytosis is due to a local stimulation of certain glandular areas. Thus in the leucocytosis of digestion, of intestinal diseases of children, we refer it to the excitation of the lymphatic apparatus of the intestine, in tuberculin lymphaemia we recognise mainly a reaction of the diseased lymph glands. Hence we conclude that a lymphocytosis appears when a raised lymph circulation occurs in a more or less extended area of lymphatic glands, and when, in consequence of the increased flow, more elements are mechanically washed out of the lymph glands. The pilocarpine lymphocytosis does not contradict this view, for pilocarpine causes extraordinary though transient variations in the distribution of water, whereby the inflow into the blood of fluid containing lymph cells is increased. We therefore regard lymphocytosis as the result of a mechanical process; whilst leucocytosis is the expression of an active chemiotactic reaction of the polynuclear elements.

This view finds its best support in the fact that the polynuclear leucocytes possess lively amoeboid movement, which is completely wanting in the lymphocytes.

Corresponding to the absence of contractility in the lymphocytes it is also observed that in inflammatory processes in contradistinction to the polynuclear neutro-and oxyphils, the lymphocytes are not able to pass through the vessel wall. A very interesting experiment on this point was described by Neumann years ago. Neumann produced suppuration in a patient with lymphatic leukaemia, in whom the blood contained only a very small number of polynuclear cells. Investigation of the pus shewed that it consisted exclusively of polynuclear cells, and that not a single lymphocyte had come into the exudation, although this kind of cell was present so abundantly in the blood.

Histological examination of all fresh inflammatory processes, in which mainly polynuclear elements are found, leads to accordant results. It is well known that small-celled infiltration occurs in the later stage of inflammation, apparently consisting of lymph cells; nevertheless this does not in the least prove that these lymphocytes have emigrated here from the blood vessels. This is not the place to enter into the very extensive controversy on this point. We are content to refer to the most recent very thorough paper of Ribbert. Ribbert regards these foci of small-celled infiltration as the analogues of the lymphatic nodules, and explains their origin by an increase in size of the foci of lymphatic tissue, normally present, though in a condition but little developed.

It consequently follows from clinical and morphological researches, as well as from the observations on inflammatory processes, that the lymphocytes are in no way connected with the polynuclear leucocytes. We shall reach the same result in another way in the following section.

([gamma]) The Bone-marrow.

The spleen and lymphatic glands were at first regarded as the sole places of formation of the blood corpuscles. The almost simultaneous researches of Neumann and Bizzozero first attracted general attention to the importance of the bone-marrow. These authors showed that the early stages of the red blood corpuscles are produced there; a discovery which was quickly and generally recognised, and which soon became pathologically useful through the observations of Cohnheim and others. In this connection the observation was of great value, that after severe loss of blood the fatty marrow of the larger hollow bones again changes to red marrow, as it is evidence of the increased demands on the regenerative function of the bone-marrow.

We are unaware of a second place of formation of the red blood corpuscles in man. In other mammalia however, as we have above mentioned (see page 99), the spleen may also take a small share in the production of erythrocytes. The type which the normal blood formation follows in adults, and the deviations therefrom shewn in pernicious anaemia, have been described in the chapter on the red blood corpuscles. Ehrlich's view that the blood formation in pernicious anaemia belongs to a different type, which is analogous to the embyronic, was also described there.

In this section we have therefore to deal chiefly with the white blood corpuscles and their connection with the bone-marrow. In man as in a large number of animals (for example the monkey, guinea-pig, rabbit, pigeon and so forth) the bone-marrow exhibits the peculiarity that the cells it produces bear a specific granulation, in sharp contrast to the lymphatic glandular system, which contains elements free from granules, in the whole animal series.

The granulated cells of the bone-marrow fall into two groups.

The first group of the cells with "special granules" is very important since it constitutes a characteristic for certain species of animals. According to the class of animal they shew different tinctorial and morphological properties. Man and monkey for example have neutrophil granulation; guinea-pig and rabbit the pseudo-eosinophil granulation described by Kurloff; in birds we find two specific granulations present side by side, which both are oxyphil, and of which one is imbedded in the protoplasm in crystalline form, the other in the form of granules.

The kinds of special granulations so far investigated have the common property, that they stain in acid and neutral dyes respectively; they shew a much smaller affinity for the basic dyes. The fact that they greatly exceed the other elements of the bone-marrow in all classes of animals, is evidence of the importance of these granules.

The second group of bone-marrow cells contains granules which we find in the whole vertebrate series from the frog to man, and which therefore are not characteristic for any one species of animal. They are, (1) the eosinophil cells, (2) the basophil mast cells.

The bone-marrow forms which are free from granules consist mostly of mononuclear cells of different type. They are not nearly so numerous, or so important as the granulated kind, more especially as the first and predominant group.

Amongst the granule-free forms the giant cells deserve special mention, for they are an almost constant constituent of the bone-marrow of the mammalian class. According to the recent researches of Pugliese the giant cells are considerably increased after extirpation of the spleen in the hedgehog; an organ of quite extraordinary size in this animal and doubtless therefore possessing important haematopoietic functions.

Pugliese asserts that in the hedgehog after splenectomy the nucleated giant cells pass into leucocytes by amitotic nuclear division. Unfortunately in his preliminary communication there are no notes of the granules of the bone-marrow cells.

On examining a stained dry preparation of the bone-marrow of the guinea-pig, rabbit, man, etc. it is seen that the characteristic finely granular cells are present in all stages of development, from the mononuclear through the transitional to the polynuclear (polymorphously nucleated) forms, which we meet with in the circulating blood. A glance at a preparation of this kind shews that the bone-marrow is clearly the factory where typical polynuclear cells are continuously formed from the granule-containing mononuclears.

Here also the same process of ripening can be seen in the polynuclear eosinophil leucocytes.

Ehrlich has been able by special differential staining to bring forward proof that the constitution of the granulation changes during the metamorphosis of the mononuclear to the polynuclear cells. In the young granules there is prominent a basophil portion that becomes less and less marked as the cell grows older. The pseudo-eosinophil granules of the mononuclear cells, of the guinea-pig for example, stain bluish-red in eosine-methylene blue after long fixing in superheated steam: in the transitional stages this admixture is gradually lost, and finally completely vanishes in the granules of the polynuclear leucocytes which stain pure red. Analogous observations may be made in the eosinophil cells of man and animals, and in the neutrophils of man. Hence it is even possible to decide whether an isolated granule belonged to an old or to a young cell.

It is still impossible to judge with certainty the rate at which the ripening of the mononuclear to the polynuclear cells proceeds, or further to decide if the ripening of the granules always runs parallel in point of time with that of the whole cell. On the grounds of our observations we would suppose that in general the two processes run their course side by side, but that in special cases the morphological ripening of the cell may proceed more rapidly than that of the granules. It is particularly easy to observe this point in eosinophil cells. Ehrlich had already mentioned in his first paper (1878) that side by side with the typical eosinophil granules isolated granules are often found which shew a deviation in tinctorial properties: for instance, they stain more of a black colour in eosine-aurantia-nigrosin; in eosine-methylene-blue, bluish-red to pure blue. Ehrlich had already described these as young elements in his first paper. The same differences are found more sharply marked in leukaemia even in the circulating blood, in the neutrophil as well as in the eosinophil group. Ehrlich has repeatedly found in leukaemic blood polynuclear eosinophil cells, whose granules must almost exclusively be regarded as young forms[15].

Ehrlich regarded these as typical examples of a relative acceleration of the morphological ripening of the cells, as compared with the development of the granules.

In normal blood we find only the ripe forms of the specific granulated cells of the bone-marrow. The mononuclear and transitional forms of the neutrophil group, do not under normal circumstances pass over into the blood-stream.

Ehrlich regarded the mononuclear neutrophil granulated cells as characteristic for the bone-marrow, since they are found exclusively in the bone-marrow, never in the spleen or lymph glands, and for this reason named them "myelocytes," [Greek: kat' exochen][16]. When myelocytes, no matter of what size, appear in considerable numbers in the blood of an adult, a leukaemia of myelogenic nature is nearly always present. (For the very rare exceptions to this rule, which it may be added can never be confused with leukaemia, see pages 77, 78.)

Exactly similar conditions hold good for the eosinophil cells, in as much as the singly nucleated forms, which one may call eosinophil myelocytes, occur, almost exclusively, in leukaemic blood. These forms, which were first recognised by H. F. Mueller, are however of less importance, for in myelogenic leukaemia the chief part of the foreign admixture of the blood is made up of Ehrlich's myelocytes.

Very important conclusions on the interesting question of leucocytosis can be drawn from these observations. Bearing in mind that polynuclear neutrophil cells are developed and stored up only in the bone-marrow, that in ordinary leucocytosis only the polynuclear forms are increased in the blood-stream, it is evident that leucocytosis is purely a function of the bone-marrow, as Ehrlich has always insisted with all distinctness. It is only on this assumption that the frequently sudden appearance of leucocytosis, as has so often been observed in morbid and experimental conditions, can be satisfactorily explained. In these cases the space of time, amounting often only to minutes, is far too short for a new formation of leucocytes to be conceivable; there must be places in which these cells are already completely formed, and able thence to emigrate on any suitable stimulus. This place is single, and is the bone-marrow alone. Here all mononuclear forms gradually ripen to the polynuclear contractile cells, which obey each chemiotactic stimulus by emigration, and which thus bring about sudden leucocytosis.

The bone-marrow thus fulfils, amongst others, the extremely important function of a protective organ, by which definite injurious influences which affect the organism may be quickly and energetically combated. Just as in a fire-station ample means of assistance is continuously in readiness immediately to answer an alarm from any quarter.

We wish to insist once more, that the large mononuclear leucocytes and the transitional forms of the normal blood are not concerned in the increase in ordinary leucocytosis; in leucocytosis of high degree their relative number may indeed be lowered, in consequence of the exclusive increase of the polynuclear cells. It appears then that these elements do not react to chemiotactic stimuli, and that possibly they reach the blood by entirely different ways than the polynuclears do.

We believe that these non-granulated mononuclear cells of man are to be regarded as analogous to those of the guinea-pig described by Kurloff (see page 86). The mononuclear cells of man however are finally transformed into the neutrophil granulated cells, whilst the cells of Kurloff remain free from granules in the course of their metamorphosis. In acute leucocytosis in the guinea-pig only the pseudo-eosinophil polynuclear cells are increased, which wander as such out of the bone-marrow, but not the polynucleated non-granulated forms, which but slowly grow to maturity in the blood. Thus the peculiarities of guinea-pig's blood, in which two kinds of polynuclear cells are recognisable, throw light upon the corresponding conditions in human blood. The distinction in the latter is more difficult, since it is not evident in this case that the fully formed polynuclear neutrophil leucocytes have a twofold origin: for the majority wander fully formed from the bone-marrow into the blood, and only a considerably smaller number grow to maturity within the blood-stream from the mononuclear and transitional forms.

No definite statement can as yet be made as to the places of formation of the non-granulated large mononuclear leucocytes.

Kurloff has demonstrated, that in the guinea-pig these cells are present both in the bone-marrow and in the spleen, but that after extirpation of the spleen the absolute number does not change. The bone-marrow then in the guinea-pig can also preserve the balance of the large mononuclear, non-granular cells in the blood.

The numbers we found in our blood investigations in man after splenectomy were also normal. We may then doubtless assume that the large mononuclear granuleless cells of human blood also arise for the most part from the bone-marrow. In this tissue they are to be picked out in the medley of the different kinds of cells only with the utmost difficulty, owing to their small number and their but little characteristic properties. Consequently an exact investigation of their origin could probably only be successful if it were possible experimentally to produce a disease in which these forms in particular underwent important increase. This advance is not quite hopeless, since in man at least an absolute increase of the large mononuclear cells is observed in the post-febrile stage of measles.

On the grounds merely of microscopical investigations we conclude that the bone-marrow is by far the most important of the blood-forming organs, for its function is the exclusive production of red blood discs as well as of the chief group of the white corpuscles, the polynuclear neutrophil.

The physiological, experimental investigation of the functions of the bone-marrow offers insurmountable difficulties. An exclusion of the whole bone-marrow or of larger portions only is an impossible operation. Nor can we ascribe any value to the researches which endeavour to obtain a result by comparative enumerations of the arterial and venous blood of a bone-marrow area. J. P. Roietzky working under Uskoff's direction has recently made counts of this kind in the dog, from the nutrient artery of the tibia and the corresponding vein. He found that the number of white corpuscles of the vein is slightly greater, that on the other hand the absolute number of "young corpuscles" (Uskoff), i.e. of the lymphocytes, has been considerably diminished, whilst the number of "ripe" corpuscles, which for the most part correspond to our polynuclear, is considerably increased. He gives the following table:

- Total number Young Ripe Old corpuscles corpuscles corpuscles - Arterial blood 15000 1950 (13%) 840 (5.6%) 12210 (81%) Venous " 16400 656 (4.0%) 2788 (17.0%) 12956 (79.0%)

The argument based on figures such as these assumes that the function of the bone-marrow is continuous; an assumption which Uskoff indeed seems to make.

But if the bone-marrow is constantly absorbing the lymphocytes to such an extent, it is quite incomprehensible how the normal condition of the blood can be preserved, bearing in mind the extent of the bone-marrow and the rate of the circulation. All evidence indeed tends to shew that on the contrary the bone-marrow performs its functions discontinuously, inasmuch as elements continually grow to maturity in the bone-marrow, as we have above explained, but they only emigrate at certain times as the result of chemical stimuli. It is obvious a priori from this consideration how inconclusive must be the results of experiments such as these of Roietzky[17].

Far more important for the elucidation of the function of the bone-marrow are clinical observations on cases in which considerable portions of the bone-marrow are replaced by tissue of another kind. We may best divide the observations on this point into two groups: 1. malignant tumours of the bone-marrow, 2. the so-called acute leukaemia.

There are unfortunately very few available observations as yet upon the first group. Still rarer are the cases in which as is necessary the whole bone-marrow has been subjected to an exhaustive examination, which alone affords adequate evidence of the extent of the defect.

Amongst the changes of the bone-marrow arising from tumours one may distinguish two groups, according to the nature of the condition of the blood. The first type is exemplified by a case of Nothnagel published in his work on lymphadenia ossium. Here during life the blood shewed, in the main, the features of a simple severe anaemia; but in addition isolated normoblasts, small marrow cells, and moderate leucocytosis. The autopsy, at which the whole skeletal system was subjected systematically to an exact examination, shewed a complete atrophy of the bone-marrow, and replacement of the same by the tumour masses. In this case then the condition of the blood in vivo is satisfactorily explained by the absence of function of bone-marrow. Nothnagel conjectured that the formation of the scanty nucleated red blood corpuscles occurred vicariously in the spleen, that of the leucocytes in the lymph glands.

In the second series to which the cases of Israel and Leyden, as well as the recently published one of J. Epstein from Neusser's wards, belong, the blood shews, besides the usual anaemic changes, other anomalies which are peculiar partly to pernicious anaemia, partly to myelogenic leukaemia. In Epstein's case of metastatic carcinoma of the bone-marrow, there was found a considerable anaemia, with numerous nucleated red blood corpuscles both of the normo- and megaloblastic type; their nuclei presented the strangest shapes, due not merely to typical nuclear division, but also to nuclear degeneration. The white blood corpuscles were much increased, their proportion to the red was 1/25 to 1/40; the increase concerned in the main the large mononuclear forms, which bore for the most part neutrophil granulation, and were therefore to be called myelocytes. In all the specimens, only two eosinophil cells were found[18].