Procaine was injected intravenously to the normal and the eviscerated rabbits and the concentration of procaine and PABA in the blood was measured. Moreover, the decomposition of procaine in plasma and homogenated liver cells was investigated. The experimental data led us to the following conclusions. Procaine in the blood will be liberated from its ester conjugation at the rate in proportion to about 2 powers of concentration. In the blood most of procaine conjugate rapidly with, perhaps, plasma proteins, but its decomposition product, p-aminobenzoic acid, does not so. The liver is comparatively poor in activity to decompose procaine, but rich in that to conjugate. In the eviscerated rabbits PABA accumulates in the body. Procaine is destroyed chiefly by the blood, though. the disposition of its decomposition products depends greatly upon the liver. Very little of procaine is excreted by the kidney, and most of PABA and its conjugation substances are excreted by it.
