1. The exaggeration of "hyaline droplet" formation observed in the renal lesion of epidemic hemorrhagic fever when treated with the infusion of large amounts of human serum albumin and the histochemical characteristics of the droplets so formed afford evidence towards their identification with the protein absorption droplets of experimental procedures and with those that occur in other renal diseases.
2. Protein absorption droplets (hyaline droplets) are the visible aspect of pathological modifications of a physiological process; i.e., the continuing reabsorption of plasma proteins by the proximal convolutions.
3. The mitochondria of the renal cells are directly involved in both the physiological and the abnormal reabsorption and disposal of the plasma proteins; the absorption droplets are a complex of reabsorbed proteins and mitochondrial substances and enzymes; they result whenever disposal is at a rate insufficient to prevent accumulation.
4. Failure of intracellular disposal of reabsorbed protein is determined by (a) the quantitative and qualitative characteristics of the protein and (b) by the functional state of renal cell.
5. Various factors in renal disease that result in disturbances of reabsorption and of intracellular disposal, both with and without droplet formation, are described.