acid and neutral dyes,
and hence in triacid and haematoxylin preparations the small lymphocytes
are seen chiefly as lightly stained nuclei, apparently free. In the
larger cells the protoplasm can be seen even in these preparations to be
slightly stained. By the aid of the iodine-eosine method the reaction of
the protoplasm of the lymphocytes is shewn to be strongly alkaline. They
do not contain glycogen.

These properties taken as a whole constitute a picture completely
characteristic of the lymphocytes; and these elements can thereby be
diagnosed and separated from other forms, even when their size varies.
Generally speaking, these cells, as above mentioned, are distinguished
in the blood of the healthy adult by their small size, approximating to
that of the red blood corpuscles. In the blood of children on the
contrary larger forms are found even in health; and in lymphatic
leukaemia particularly large forms occur, which are mistaken in various
ways by unpractised observers. Thus Troje's "marrow cells" still figure
in the literature, but have absolutely nothing to do with the marrow.
They are large lymphocytes, as was established by A. Fraenkel years
afterwards.

[Illustration: Fig. 1.

Fraying out of the protoplasmic border in large lymphocytes. Free plasma
elements formed by budding. ("Plasmolysis.")

(From a photograph of a preparation from chronic lymphatic leukaemia.)

_To face page 72_]

[Illustration: Fig. 2. (From Rieder's Atlas.)

Metamorphosis of the nucleus of the lymphocytes. (Combined picture from
a preparation from acute leukaemia.)

_To follow Fig. 1_]

In the normal blood of adults the number of the lymphocytes amounts to
about 22-25% of the colourless elements.

Increase of the lymphocytes alone occurs, but in comparison with that of
the other forms, much more seldom, and will be conveniently called by
the special names of "lymphocytosis" or "lymphaemia."

2. Sharply to be distinguished from the lymphocytes is the second group:
the "large mononuclear leucocytes." These are large cells about twice to
three times the size of the erythrocytes. They possess a large oval
nucleus, as a rule eccentrically situated and staining feebly, and a
relatively abundant protoplasm. The latter is free from granulations,
feebly basophil, and in contrast to the protoplasm of the lymphocytes
stains less deeply than the nucleus. This group is present in normal
blood in but small numbers (about 1%). They are s