Demonstration of basophilic stippling in erythrocytes.

The recognition of basophilic stippling in erythrocytes depends largely on subjective factors such as visual acuity and experience. An expert may observe stippling in the ordinary blood film stained with B.D.H. Leishman stain diluted with water at pH 6.8 to 7.0 when less expert observers may see nothing. If one could increase contrast between the stippling and its background it would become easier to recognize. This increase in contrast can be achieved by dark-ground illumination. A stained particle under dark-ground illumination reflects that light which would be absorbed were it to pass through the stain ; it therefore appears to emit light of a colour complementary to that which it possesses by transmitted light. The thionins and thionols which constitute the basic components of all Romanowsky stains in their blue form absorb orange light, so that particles stained with them appear orange under dark-ground illumination. The red cell, if properly stained, has a pale, yellowish-green outline, within which may occur the orange-coloured dots of light which represent basophilic stippling: these particles are easily differentiated from other particles and debris.