The spreading of leukocytes released from their liquid environment.

It is known that while leukocytes in conventional blood smears reveal their structures, in smears of erythrocyte-free suspension (EFS) they show a tendency to pyknosis. From the present study it appears that: 1. When any leukocyte suspension is subjected to drying on slides the cells undergo shrinkage (pyknosis in stained state) because their water content is extracted by the suspending fluid that is rendered increasingly hypertonic during drying. 2. When the leukocytes, which while floating within physiological fluids are ball-shaped, are entirely released from their suspending fluid, they suddenly spread into flat cells because the capillary force between the cell membranes and glass overcomes the surface tension of the cells. 3. In contrast to shrunken or even normal (spherical) cells, spread cells are able to display their morphology. Using the smear technique, the cell density of the suspension will determine whether spreading or shrinkage are to occur; with normal blood (high density) the release and consequently the spread are achieved; with EFS (usually of low density) an inadequate release and consequently shrinkage occur. 4. A device (cell spreader) for spreading leukocytes of EFS is presented.