Stained films show no changes in very mild cases. In moderate cases variations in size and shape of the red cells and polychromatophilia occur. Very severe cases show the same changes to greater degree, with addition of basophilic degeneration and the presence of normoblasts in small or moderate numbers. Megaloblasts in very small numbers have been encountered in extremely severe cases. Blood-plaques are usually increased. 2. Primary Anemia.--The commonly described varieties of primary anemia are pernicious anemia and chlorosis, but splenic anemia may also be mentioned under this head. (1) Progressive Pernicious Anemia.--It is frequently impossible to diagnose this disease from the blood examination alone. Severe secondary anemia sometimes gives an identical picture. Remissions, in which the blood approaches the normal, are common. All the clinical data must, therefore, be considered. Hemoglobin and red corpuscles are always greatly diminished. In none of Cabot's 139 cases did the count exceed 2,500,000, the average being about 1,200,000. In more than two-thirds of the cases hemoglobin was {206} reduced to less extent than the red corpuscles: the color-index was, therefore, high. A low color-index probably indicates a mild type of the disease. The leukocyte count may be normal, but is commonly diminished to about 3000. The decrease affects chiefly the polymorphonuclear cells, so that the lymphocytes are relatively increased. In some cases a decided absolute increase of lymphocytes occurs. Polymorphonuclear leukocytosis, when present, is due to some complication. [Illustration: FIG. 84.--_A_, Normal blood; _B_, chlorosis; _C_, pernicious anemia. The plate shows the sharp contrast between cells rich in hemoglobin and the pale cell of chlorosis, and also the poikilocytosis and marked variations in size noted in pernicious anemia. A normoblast and megaloblast also appear. Stained smears (from Greene's "Medical Diagnosis").] [Illustration: PLATE VIII. EXPLANATION OF PLATE VIII. Fig. 1.--Preparation from an advanced case of progressive pernicious anemia from unknown cause: _a_, Megaloblasts or gigantoblasts; the protoplasm shows marked polychromasia; _b_, stained granules in erythrocytes with normally stained protoplasm; _c_ and _d_, polychromatophilic degeneration; _e_, megalocytes; _f_, normocytes. Fig. 2.--Preparation from the same case taken some time later while the patient was subjectively and objectively in perfect health: _a_, Punctate erythrocytes with normal and anemic degenerated protoplasm; _b_, polynuclear leukocyte; _c_, normal red blood-corpuscles; _d_, somewhat enlarged erythrocytes.