Blood is obtained by a small puncture, and slides smeared and allowed to dry. Immediately on drying the slip is flooded with the stain, and allowed to remain for two minutes. This causes fixation. At the end of the two minutes the stain is diluted with an equal volume of distilled water, and allowed to remain on for a further three minutes. At the end of this time the stain is poured off, and the slip washed in distilled water for another three minutes, or until the characteristic purple-violet appearance is produced. It is better to examine such films with an oil-immersion lens, the oil being placed directly upon the films, and not covered with a cover-slip, as the action of Canada balsam tends to decolorize the blue. If such specimens are required to be kept, the oil may be washed off with xylol. It is possible to observe basophile staining with a good sixth, but an oil-immersion lens gives much the best result. The typical staining produced by this means gives darkish bodies scattered about the red corpuscles, staining sometimes deeply as the nuclei of the white corpuscles. In other cases the appearance is like that of fine dust scattered throughout the cell. In addition to these two forms, the whole red cell may take on a slight generalized lilac tint, the normal cells remaining free from granules, and stained red by the eosin. Search of 100 fields of the microscope should be made, and if no basophile granules are found in such fields it is unlikely that they will be found. Basophile staining is not more pathognomonic of lead poisoning than of any other form of anæmia, but may be regarded as a highly important confirmatory diagnostic sign. A differential count of the leucocytes present may be also made on the same film in which basophile staining is observed; 300 should be counted at least. In a typical case of lead poisoning it is found that diminution in the polymorphonuclear leucocytes has taken place with a corresponding increase of the lymphocytes, and possibly also the large mononuclears, and probably a slight increase in the number of eosinophiles. This hæmatological method of diagnosis is of the utmost importance in lead poisoning. A differential count such as is given on p. 137, showing a large diminution in the polymorphonuclears, an increase in the lymphocytes, evidence of changes in the red cells, consisting of basophile staining, alteration in the shape of individual cells, poikilocytosis, with vacuolation, is strong presumptive evidence of lead absorption. To complete the hæmatological examination, the hæmoglobin should be estimated. This is best performed with Haldane’s instrument--an exceedingly simple one to use. The estimation of the number of red cells and white cells present is useful, but does not by any means give such valuable information as does the differential count and search for basophile granules.