1. Congo red injected in vivo together with uric acid gives rise to more intense and diffuse red coloring in rats, especially in the subcutaneous and peri-articular tissues, than is the case in control rats injected simply with dye.
2. Uric add added in vitro to solutions of Congo red or trypan blue increases the speed of diffusion of these dyes, both through gelatin and the animal membranes (dialyzers).
These results support a view long maintained by Professor Rondoni (25), namely, that some factor of an endothelial-capillary nature must be taken into consideration in manifestations of hyperuricemia and of gout.