It has been shown that in two species of lizards there is no change in the lactic acid content of blood as body temperature changes. This is not in accord with the observations of Austin, Sunderman and Camack ( '27) on the alligator. This reptile was found to have a much higher lactic acid concentration a t a temperature of 35O than at 9". At the same time the alkaline reserve was diminished more by this temperature change than would have occurred in vitro. They note, however, that the animals were combative at the higher temperature, and intimate that their results may have been complicated thereby. It seems not improbable that lactic acid should accumulate in anaerobic activity of reptiles, as it does in man. Thus in our own study of the crocodile and caiman (Dill and Edwards, '31) at an environmental temperature of 29" there were large variations in blood lactate apparently related to activity. At constant pCO,, however, the sum of lactate and bicarbonate was roughly constant.
This apparent variability of response to temperature change seemed to warrant a further study of alligator blood. Our curiosity was also aroused concerning the acid effect on the affinity of hemoglobin for oxygen. I n the two lizards studied the effect was like that in man rather than that in the crocodile. Hence studies have been carried out similar to those of Austin but also including observations on the properties of hemoglobin.