Conclusions Low concentrations of Triturus toxin had no effect on the respiratory rate of rat brain, kidney and liver slices in vitro. In the presence of 85 M.U. per ml in the case of liver, and of 850 M.U. per ml in the case of kidney and brain slices, slight transient stimulation of respiration occurred, but it is not clear that this could be attributed to the action of the toxin.