WHITE BLOOD- CORPUSCLES 83 



To provide against evaporation, run a drop of sweet oil around the 

 edge of the cover. 



The blood -plates may be found, after careful search, bearing 

 the relation to the red corpuscles seen in Fig. 58. 



WHITE OR COLORLESS BLOOD -CORPUSCLES 



The white blood -corpuscles are also called leucocytes. In fresh 

 preparations they are seen to be perfectly colorless, nearly spherical 

 cells, often slightly granular. The nucleus is distinguished with 

 difficulty unless reagents are used. The leucocytes are not all of 

 the same size. The larger ones are the more numerous. If they 

 are watched carefully, the larger ones may be observed to change 



FIG. 58. HUMAN BLOOD PRESERVED WITH OSMIC ACID. 



A. Colored corpuscles. 



B. Colorless corpuscle. 



C. C, C. Groups of plaques. (X 400 and reduced.) 



their shapes slowly. This movement is a property belonging 

 to their protoplasm called amoeboid movement.* Portions of 

 the protoplasm are slowly extended outwards, making projections 

 called pseudopodia, which may be 'drawn in again. By means 

 of this movement the leucocytes can travel slowly from one part 

 of the field to another. They are more active when the slide is 

 warmed slightly. 



*The Amoeba is an exti-emely simple unicellular animal (Protozoon), which is found in 

 the water of ponds. It is usually much larger than the white blood -corpuscle, and its move- 

 ment is ordinarily very active and easily seen. The student should examine specimens of 

 water and watch the movement of the Amoeba. 



