Abstract: An improvement in the degree of separation of constituent cell layers in a centrifuged sample of human blood is achieved by decreasing the natural water content of the red blood cells to increase their density or specific gravity. Thus the red cell layer packs more tightly and separates more completely from the next lighter cell layer adjacent thereto, i.e., the granulocyte layer.

Abstract: An apparatus and method for measuring the linear extent and hence the concentration of several constituent blood cell types which are contained in the buffy coat of a centrifuged sample of anticoagulated blood.

Abstract: A device for use in checking and/or calibrating the accuracy with which a blood constituent concentration measuring instrument is operating. The device includes a capillary tube size member having annular bands marked on its outer surface. The bands are of predetermined axial extent and simulate centrifuged blood cell or other constituent layers. The axial dimension of each band is measured on the instrument which provides a visual indication of corresponding blood cell count. The blood cell count indicated by the instrument is then compared to the known blood count corresponding to the predetermined axial extent of the particular band measured. This device may be used to calibrate the instrument or determine the accuracy with which the instrument is operating.