Abstract
1. The refractive neutral red staining particles seen in unstained or supravitally stained lymphocytes have the following properties: They are birefringent and show a polarization cross. Their refractive index is 1.45 to 1.48. They are soluble in fat solvents, in cold alcohol and in strong but not weak acid or base. They stain with lipid stains and basic dyes and are increased in number by the action of neutral red on supravital preparations of blood cells.
2. These properties are interpreted as indicating that the particles seen in human lymphocytes are composed of lipid material. It is probable that much of the fat is of the polar-apolar type, possibly phospholipid in nature.
3. The refractive particles are believed to be the counterparts in human lymphocytes of the phospholipid-containing droplets which occur in somatic cells of other mammalian tissue.
4. The significance of the increase in numbers of these droplets under certain conditions and their relationship to the Golgi apparatus are discussed.
