Fig. 2. (From Rieder's Atlas.)
Metamorphosis of the nucleus of the lymphocytes. (Combined picture from a preparation from acute leukæmia.)
To follow Fig. 1
In the normal blood of adults the number of the lymphocytes amounts to about 22-25% of the colourless elements.
Increase of the lymphocytes alone occurs, but in comparison with that of the other forms, much more seldom, and will be conveniently called by the special names of "lymphocytosis" or "lymphæmia."
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 hæmorrhagic 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.
