proportionally large number of parasites in any given field, lends itself to this, as does the fact that the hæmozoin shows up very distinctly in the homogeneous sheet of free hæmoglobin.
Phagocytosis and pigmented leucocytes.—Striking examples of phagocytosis are often witnessed in malarial blood. So soon as a malarial parasite, whether spontaneously or as a result of pressure, escapes from the blood corpuscle in which it had developed, it becomes exceedingly liable to attack by the phagocytes. More especially is this the case with the flagellated organism; this body seems to have a powerful attraction for the phagocytes, which are often seen to travel long distances to attack it.
Pigmented leucocytes that is to say, leucocytes containing grains or blocks of hæmozoin are very often encountered; they can best be seen in the single-layer zone during, or shortly after, fever. Leucocytes may sometimes be observed to include the hæmozoin set free by the falling to pieces of the segmented parasites. Often they derive their hæmozoin from the remains of some sphere or flagellated body which they may have engulfed subsequently to the preparation of the slide. In peripheral blood the phagocytes are rarely, if ever, seen to attack the parasite so long as it is inside a blood corpuscle.
Both the large mono- and, very rarely, the poly-nucleated leucocytes may contain malarial pigment. Care, however, must be exercised in drawing conclusions from the discovery of black material in these bodies; in imperfectly cleaned slides, fragments of dirt, which the leucocytes rapidly take up, are apt to mislead.
Pigmented lymphocytes.—According to Metchnikoff, the lymphocyte has no phagocytic action in malaria. This observation I believe to be correct. Several writers, however, have described and figured what they regard as malarial pigment in the lymphocyte. This, I am convinced, is founded on an error in interpretation, and has arisen from ignorance of the fact that in all bloods, healthy and malarial alike, from 20 to 50 per cent, of the small mononucleated lymphocytes contain, lying in the narrow zone of
