MORPHOLOGY OF LEUCOCYTES AND RED CORPUSCLES 2I9 



You will see the droplet of blood spread itself out by capillary 

 attraction between the two cover-glasses. 



At this stage you will see whether you have taken the right 

 amount of blood or no. If you have, the drop will spread out, 

 still retaining its circular shape, until it approaches the octagon 

 formed by the intersecting edges of the two cover-glasses 



Fig. 46. 



(Fig. 47); if you have taken too little it will not reach so far, 

 and if you have taken too much it will extend further, and the 

 upper cover-glass will float loosely on the lower. 



It is necessary to lay great emphasis on the fact that the cover- 

 glasses must not be squeezed together, but must simply come 

 together by capillary attraction. 



When the drop has ceased to spread take hold of the upper 

 cover-glass with the finger and thumb of your right hand and 

 slide the two apart, keeping them in the same plane ;^ this is 

 readily done, since the cover-glasses are free to turn, being only 

 held loosely at the points. If you do not do this, either the cover- 

 glasses will break, or else the upper cover-glass be lifted from the 



