Use of dark ground microscopy in haematology

The novel combination of vital staining, quick drying of thin films, and dark ground microscopy furnishes new information about organelles, granules, and precipitates in blood cells. The preparations are permanent and give optical signals of high contrast which depend on refraction or dichroism of the object. Mitochondria are readily shown and can be counted and sized. Pilot observations suggest that mitochondria in red cells may give information about cell maturity and splenic function; that the size of lymphocyte mitochondria may reflect the state of activation of those cells; and that the sensitivity of unstable haemoglobin detection may be greatly enhanced. The method is unsuitable for the study of granulocyte mitochondria.