In 16 pairs of blood samples drawn simultaneously from the femoral artery and femoral vein of 11 unanesthetized, quietly resting depancreatized dogs, the R. Q., CO2 and O2 capacities, acetone substances, lactic acid, and pH were detd. In 3 exps., the R. Q. was below, and in 12, above 0.7; the variations could not be accounted for by changes in the acid base balance or conc, of the blood. In each exp. in which the R. Q. was below 0.7, acetone substances were liberated into the blood stream; in 10 of the 12 exps. in which the R. Q. was above 0.7, acetone substances were removed from the blood, suggesting that the ketone acids removed by the muscle were oxidized to produce the high R. Qs., while the low R. Qs. resulted from the incomplete combustion of fatty acids. If glucose is not oxidized in pancreatic diabetes, it is possible to ascribe the high R. Qs., in part, and a ketolytic effect, in its entirety, to the oxidation of lactic acid.