This is to report the effect on the blood sugar level of cats of a “heat liability,” produced by giving ice water by stomach tube, according to the method devised by Cannon. Eight animals have been used and all have given concordant results, of which those for one cat shown in the figure are typical. From inspection of the curves (and deducting the effect of the similar procedure in which water at body temperature was given), it appears that such a heat liability induces a pronounced mobilization of carbohydrates and increase of blood sugar value. In spite of the fact that the fall in body temperature is immediate, this mobilization of sugar seems to get under way slowly and is only noticeable after an hour or more. From then on it rises slowly to a maximum during the next hour or two and then, even more slowly, falls; in only two cases out of the eight did the blood sugar value return to normal within the five or six hours during which the animals were kept under observation.