Megakaryocytes in normal and in thrombocytopenic individuals; with introduction of a new system of differential count for megakarocytes.

The bone marrow specimens were secured in the usual way by sternal puncture. The amount obtained did not exceed o. cubic centimeters. Without using an anticoagulant, the material was spread on slides as in preparing blood films. Seven to ten smears were made. The smears were made thin, slightly thick, and thick. The thick ones were used to obtain a general impression of the condition of the bone marrow at the time of the biopsy. For a differential count of the megakaryocytes, those films were examined which showed a great number of these cells without morphologic distortion. It has been observed that these smears could not be used with satisfaction for the differential examination of the smaller bone marrow cells. Before sternal puncture was made, the total platelet count in the peripheral blood was determined. Either the wet smear method of Dameshek (D) or the dry method of Fonio (F) was employed, depending upon convenience. Other hematologic examinations were carried out to determine normality, or for the sake of diagnosis. The smears were fixed with Wright’s solution and stained with Giemsa’s. The number of megakaryocytes per million nucleated cells was not counted for two reasons: (z) Even in a carefully made smear the megakaryocytes, being heavier than other types of cells, tend to gather more at the initial portion. Hence, more megakaryocytes are to be found in this area than in any other