104 MANUAL OF HUMAN PROTOZOA 



and bi-concave, and stain homogeneously, except the 

 central area which is lighter in color (Fig. 27, l). They are 

 about 7.5n in diameter. Some erythrocytes show small 

 knob-like projections from their surface. These are cre- 

 nated ervthrocvtes (Fig. 27, ^), and appear in drawn-out 

 normal blood. In addition to the normal erythrocytes, 

 macrocytes, about 10-14n in diameter (Fig. 27, 3) and 

 microcytes, 2-6m in diameter (Fig. 27, 4) may be present in 

 the blood of persons suffering from anaemia including 

 subtertian malaria. Some erythrocytes may be nucleated 

 (Fig. 27, 5); they are called normoblasts. Some erythrocytes 

 may show basophilic dots (Fig. 27, ^), others chromatin 

 dots (Fig. 27, "), and still others Cabot's rings, either ir- 

 regularly rounded (Fig. 27, 8) or in form of an 8 (Fig. 

 27, ^). Sometimes in the blood of tertian malaria patients 

 may appear large erythrocytes with a yery large eccenti'i- 

 cally placed yacuole, resembling half moon in shape with 

 a somewhat undulating outline, which simulates a trypano- 

 some (Fig. 27, 10). 



Blood platelets. Thrombocytes are rounded disc-shaped 

 bodies with indistinct margins and are 1-3m in diameter. 

 They may be found singly in clusters, or in chains (Fig. 

 27, 11). They stain bluish with red-stained granules in 

 center. Occasionally filamentous processes may be seen. 

 When an isolated platelet is attached to an erythrocyte, it 

 may simulate a young schizont of Plasmodium, but there 

 is always a clear zone around the platelet by which it can 

 be identified as such (Fig. 27, 12). 



Leucocytes. There are many kinds. The main types are 

 as follows: 



Neutrophile polymorphonuclear leucocytes (Fig. 27, i"^). 



