Within recent years the development of numerous modifications of the Romanowsky stain, by which blood smears may be fixed and stained in a few minutes, has limited the use of Ehrlich's triacid stain in many laboratories. The former, it is true, are far preferable in the study of pathologic changes in the erythrocytes, as cell nuclei, nuclear particles, polychromatophilia, basophilic granules, and Cabot's ring bodies, as well as certain parasites, are demonstrated to better advantage than with any other single stain. With Ehrlich's triacid, ring bodies and basophilic granules are not revealed, and polychromatophilia is shown very imperfectly. In studying the leukocytes, however, the Romanowsky stains are not to be compared with Ehrlich's triacid, and it seems unfortunate that they are so widely used at the present time in differential leukocyte counting.
CLASSIFICATION OF LEUKOCYTES
The generally accepted classification of the leukocytes is that suggested by Ehrlich, based on the