During the course of a study on inorganic salt metabolism in dogs and rats which has been in progress in the Department of Pediatrics of the University of California Medical School for the last two years, it has been observed that rickets develops in young puppies on a diet which appears to be adequate in respect to protein, fat, carbohydrate, inorganic salts and vitamins, but possesses a relatively high potential alkalinity. Parallel experiments with rats on the same diets have invariably resulted in normal bone development. Schabad1and others have shown that in infants with active rickets the distribution of calcium and phosphorus between the urine and the feces is different from that which occurs in normal individuals—there being a much higher proportion of the total excretion lost in the feces of the former than in those of the latter. Experimentally, we have confirmed this, and have furthermore been