This variation of pigment color may be due to the effect of chromatin staining, as the black of the pigment is the same in male and female gametes in fresh blood preparations.

Stained Smear Preferred.—As regards differentiation of species and cycle the examination of stained smears is more satisfactory and definite, as well as less time consuming. Still, one obtains many points of differentiation in the fresh preparation and should study such a preparation while carrying out the staining of his dried smear.

Unstained Specimen (fresh Blood)
P. vivax (benign tertian)P. malariae (quartan)P. falciparum (malignant tertian) (aestivo-autumnal)
Character of the infected red cell.Swollen and light in color after eighteen hours.About the size and color of a normal red cell.Tendency to distortion of red cell rather than crenation. Shriveled appearance. (Brassy color.)
Character of young schizont.Indistinct amoeboid outline. Hyaline. Rarely more than one in r.c. Active amoeboid movement. One-third diam. of r.c.Distinct frosted glass disc. Very slight amoeboid motion.Small, distinctly round, crater-like dots not more than one-sixth diameter of red cell. Two to four parasites in one red cell common. Shows amoeboid movement until appearance of pigment.
Character of mature schizont.Amoeboid outline. No amoeboid movement.Rather oval in shape. Sluggish movement of peripherally placed coarse black pigment.Only seen in overwhelming infections. Have scanty fine black pigment clumped together.
Pigment.Fine yellow-brown, rod-like granules which show active motion in one-half-grown schizont. Motion ceases in full-grown schizont.Coarse almost black granules. Shows movement only in young to half-grown schizont.Pigmented schizonts very rare in peripheral circulation except in overwhelming infections. Tends to clump as eccentric pigment masses almost black in color.

Stained Specimen
P. vivax (benign tertian)P. malariae (quartan)P. falciparum (malignant tertian) (aestivo-autumnal)
Character of infected red cell.Larger and lighter pink than normal red cell. Shows “Schüffner’s dots.”About normal size and staining.Shows distortion and some polychromatophilia and stippling. Rarely we have coarse cleft-like reddish dots—Maurer’s spots.
Character of young schizont.Chromatin mass usually single and situated in line with the ring of the irregularly outlined blue parasite.Rather thick round rings which soon tend to show as equatorial bands.Very small sharp hair-like rings, with a chromatin mass protruding from the ring. Often appears on periphery of red cell as a curved blue line with prominent chromatin dot. Frequently two chromatin dots.
Character of half-grown schizont.Vacuolated or Fig. 8 loop-like body with single chromatin aggregation. Schüffner’s dots.More marked band forms stretching across r.b.c.Not often found in peripheral circulation. Chromatin still compact.
Character of mature schizont.Fine pigment rather evenly distributed in irregularly outlined parasite.Coarse pigment rather peripheral- ly arranged in an oval parasite.Very rarely seen in peripheral circulation in ordinary infection. Pigment clumps early.
Character of merocyte.Irregular division into 15 or more spore-like chromatin dot segments.Rather regular division into eight or ten merozoites—Daisy.Sporulation occurs in spleen, brain, etc. Rarely in peripheral circulation. 6 to 10 irregularly placed merozoites. (In culture 32.)
Character of macrogamete.Round deep blue. Abundant, rather coarse pigment, chromatin at periphery.Round, similar to P. vivax but smaller.Crescentic, pure blue pigment clumped at center, chromatin scanty and in center.
Character of microgametocyte.Round, light green-blue, pigment less abundant, chromatin abundant and located centrally or in a band.Round like P. vivax.More sausage-shaped than crescent. Light grayish blue to purplish. Pigment scattered throughout. Chromatin scattered and in greater quantity but difficult to stain.

Central vacuolation of red cells is common in malarial anaemia and may be mistaken for nonpigmented parasites.

Malarial rings are usually peripheral and do not vary in size as one focuses up and down as do the central vacuoles.

Quinine-affected Parasite.—A very puzzling but well-recognized finding in cases treated with quinine or salvarsan is the so-called quinine-affected parasite. Such parasites lack definiteness of outline and show poor chromatin staining. The gametes do not seem to show these effects from the drug.

Certain questions connected with the life history of the malarial parasite in man which are of interest.