CHAPTER I.

THE BLOOD.

1. Changes in the Red Corpuscles.-These changes affect partly the number and partly the size, shape, or other characters of the red corpuscles.

(i.) Oligocythemia rubra, or decrease in the total quantity of red corpuscles, in which their number may sink from the 4-5,000,000 per cubic millimetre of the healthy adult to 2,000,000, or even to half-a-million and under (as in pernicious anemia, for example), occurs as a temporary condition after severe hæmorrhages, or permanently in the so-called hamic diseases (leucemia, chlorosis, and pernicious anæmia), as well as in conditions of inanition, phthisical disease, and certain intoxications and infections. The higher grades

can at once be recognised from the pale colour of the blood, and from the strikingly small number of the red corpuscles in microscopic preparations; the slighter grades only by actual counting of the corpuscles.

(ii) Macrocythemia rubra (Plate I., Fig. 3, i), or increase in the diameter of isolated red corpuscles from the normal 7.8 μ to 10 or 15, is not to be confounded with the swelling of the red corpuscles in hydramic blood. It is observed in all severe anæmias, but especially in pernicious anæmia, and sometimes also in leucemia and chlorosis.

(iii.) Microcythemia rubra (Plate I., Fig. 3, h), the occurrence of globular elements which are smaller and also as a rule of deeper colour than normal red corpuscles, and which perhaps are formed by degeneration of the latter, is present in most anæmias, a few intoxications, and also after burns and hæmorrhages of severer degree. (iv.) Poikilocytosis (Plate I., Fig. 3, g) is that condition in which the red corpuscles assume very varied forms (flask-, kidney-, anvil-, or cup-shapes), but the significance of which is still quite obscure. It is present to a moderate extent in almost all severe anæmias,

notably also in leucemia, but to a conspicuous degree in pernicious anæmia. It must not be confounded with the mulberry and thornapple forms of red corpuscle which occur very soon after the blood is drawn off, in consequence of evaporation.

(v.) Nucleated red corpuscles (Plate I., Fig. 3, k and ). These are found in severe anæmias and in myelogenic leucemia, as well as after extensive hæmorrhages. They are either of normal size (normoblasts) or considerably larger (megaloblasts), the latter indicating a bad type of disease.

2. Changes in the White Corpuscles.-The most frequent change is an increase in number, occurring either as simple leucocytosis, or as leucamia.

In normal blood the following five forms of white corpuscles occur, of which the later in series in each instance always develops from that which precedes:

(1) Small lymphocytes (Plate I., Fig. 4, a), about the size of red corpuscles, with a relatively large nucleus which stains intensely.

(2) Large lymphocytes (Plate I., Fig. 4, b), at least twice the size of the former, having nuclei which are likewise large but often stain less deeply, and a cell-body usually somewhat broader.

(3) Mononuclear transitional forms, the nucleus of which is indented in the centre, and whose protoplasm commonly already shows the first traces of the so-called neutrophil granulation.

These are larger

(4) Polynuclear leucocytes (Plate I., Fig. 3, c). than red corpuscles, and usually smaller than the large lymphocytes (No. 2), have several nuclei which take a deep colour, and usually show in their protoplasm numerous granulations which will stain only in neutral anilin colours, i.e., neutrophil granulations, these being subject to certain fluctuations in size, but still in general finer than those in the following variety of cells.

(5) Eosinophil leucocytes (Plate I., Fig. 3, d), which usually possess two less strongly-staining nuclei or one indented nucleus, and have in their protoplasm coccus-like granules, which stain readily in acid anilin colours, and are, as a rule, coarser than the granules of the preceding variety of leucocytes. The eosinophil cells are often found in a disorganised condition (c).

According to countings made with dried preparations of normal blood, the lymphocytes (Nos. 1 and 2) constitute approximately 25 per cent., and the polynuclear leucocytes 60 to 70 per cent. of the total number of white corpuscles, whilst the remainder is made up of transitional forms and eosinophil cells.

(i.) In leucocytosis, which is temporarily present during digestion, and also occurs after hæmorrhages and in various infective diseases

and cachexies, as well as very often before the death-agony, and is in general of little significance, there exists merely an increase in the numbers of the polynuclear leucocytes, or at least only of the kinds of white corpuscles normally present in the blood, in which latter case, however, the normal ratio between the percentages of the different kinds of leucocytes remains unaltered.

(ii) Leucemia is either myelogenic (myelo-splenic) or lymphatic, in either of which forms the number of white corpuscles may so increase as to equal or even exceed that of the red, while the latter are commonly diminished in amount, and show poikilocytosis.

(a) The first form of leucemia (Plate I., Fig. 3) is characterised by multiplication of the eosinophil cells (d and e), and particularly by the presence in very large numbers of round mononuclear leucocytes. These are probably derived from the marrow of bones (myelocytes, a), and differ from the large lymphocytes of normal blood, with which they might most readily be confounded, in being in general larger, sometimes even considerably so, and in the facts that their remarkably large nuclei stain still more feebly than those of the lymphocytes, and that their protoplasm usually exhibits neutrophil granulations. The constant presence of nucleated red corpuscles of normal (k) or excessive (1) size is also characteristic of this form of leucemia.

(b) In the second form (Plate I., Fig. 4), which is more rarely observed, it is only the mononuclear leucocytes of the blood (lymphocytes, a and b), especially the small forms, which are increased, and these may multiply until they constitute as much as 95 per cent. of all the white corpuscles. On the other hand, none or almost none of the nucleated red corpuscles are present, and but few eosinophil cells. After death in leucemia the so-called Charcot's crystals are met with in the blood as well as in the marrow of bones and in the spleen. These are colourless elongated octohedra, which, as is well known, are constantly present in the semen, and sometimes also in the sputum [e.g. in asthma; see p. 289].

The higher degrees of leucæmia can be recognised from characters of the blood which are apparent even to the naked eye (inasmuch as it is thinner, paler, and more turbid than normal, whilst the postmortem clots are of a reddish-grey or even yellowish-green pus-like colour), as well as in microscopic preparations from the extraordinarily large number of the white corpuscles. A slight increase in the numbers of the white corpuscles, however, can only be recognised by counting, it being borne in mind that the normal ratio of the white to the red corpuscles may fluctuate between 1 500 and 1: 1000, and that slight deviations from this ratio should scarcely be regarded as pathological conditions.

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