1. There is a practically constant desquamation of endothelial cells into the circulating blood in rabbits and man.
2. These endothelial cells represent the entire range in size of endothelium from very small cells, possibly from capillaries, up to the type of the large Kupffer cell.
3. These desquamated cells can be discriminated from monocytes.
4. There are common morphological and functional characteristics among the following cells: the clasmatocytes from the specific endothelia, such as the cells from the sinuses of the liver, spleen, and bone marrow; the clasmatocytes of the diffuse connective tissues; and desquamated endothelial cells occurring in normal and pathological blood.
5. There are four strains of white cells in the normal circulating human and rabbit blood, granulocytes, lymphocytes, monocytes, and endothelial phagocytes.