PRACTICAL DETAILS 



129 



elements in the same direction is due to currents set up in the pre- 

 paration. 



FIG. 117. Preparation showing red blood cells, hsematoblasts and strandg 

 of fibrin (after Gastou). 



Lastly it cannot be too strongly emphasized that the smallest trace of dust 

 on the slides or cover-glasses interferes materially with the examination 

 of the preparation. 



