RESULTS

Release of Bradykinin from Normal Blood by Snake Venoms and Trypsin. When the venoms of most species of snakes are put into contact with the uterus or the gut of the guinea pig, they cause a sharp increase of tonus that lasts for a long interval of time, even after repeated washings with new Tyrode solution. After relaxation, a second addition of the same dose of venom is either ineffective or produces a lesser effect, followed by a refractory state (desensitization) to any further addition of the venom. This effect, described by several workers (I 2, 13, I 5, I@, was also described for trypsin (17) by one of us. If the guinea pig gut is made refractory to the action of snake venoms and trypsin, it can be used as a suitable test organ for the release of pharmacologically active substances from biological structures. On the other hand, the plasma of certain species (dog, ox and cat) is very poor in histamine and