Intraven. injd. antipyrine is destroyed in the dog at the rate of 20-60% / hr. Nevertheless, antipyrine space may be used for the detn. of total body water in the dog, because the distr. of antipyrine appears to be essentially complete after 10 min. Dogs in adequate nutritional status are found to have antipyrine spaces of 53.9%-67.9%. The avg. value obtained from 8 normal dogs was 59.9%. Inadequate nutrition and emaciation result in an increase in the antipyrine space, a result consistent with the idea that body water is related more closely to lean body mass than to body wt.