1) The fact that potentiation of the action of epinephrine after small doses of endotoxin was observed only to a slight extent in the presence of barbiturate, and not at all when ether or decapitation without anesthesia was employed to prepare the ear for perfusion, leads us to question whether the effect described by Zweifach, Nagler and Thomas is actually a direct potentiating action of ... [Show full abstract] epinephrine. We have no explanation as to how endotoxin might antagonize a barbiturate effect. 2) One point is noteworthy, our preparations in general had a much lower control epinephrine threshold than those reported for the perfused rabbit ear by above mentioned workers. 3) Our results are entirely uniform in showing that no reversal of epinephrine action after the large doses of endotoxin occurred, even with barbiturate anesthesia. We have no explanation to offer for this failure to confirm Zweifach et al.