The first quantitative studies of pulmonary and cutaneous respiration in the amphibians were made on Rana esculenta and Rana temporaria by Krogh (1904). He inserted a cannula connected to an air pump into the trachea and analyzed separately the air forced through the lungs by the pump and the air surrounding the frog. He was able to show that in R. temporaria the lungs and skin are both important in respiratory exchange but in somewhat different ways. Oxygen enters through the lungs whereas carbon dioxide is excreted through the skin. Oxygen intake through the skin is determined solely by physical limitation while carbon dioxide excretion may vary with environmental charges. Krogh concluded that in R. temporaria the lungs dominate in oxygen consumption over the skin in a ratio of 3:1. In R. esculenta the ratio was 1:1. This probably correlated with the more aquatic habitat of R. esculenta. In the salamander, Ambystoma maculatum, Hutchison (1963) found that not only is eighty percent of the carbon dioxide produced released through the skin but the skin is also responsible for more than fifty percent of the total oxygen uptake at 15°C and below. Rana catesbeiana tadpoles were used in these experiments. They were obtained from the Mokelumne River on Highway 88, two miles west of Clements, California The function of the lungs in Rana catesbeiana tadpoles was studied.