Summary: Frogs do not seem to show acute allergic manifestations as do mammals and it is suggested that this is due to certain pecularities of physiology and innervation of the smooth muscle fibers. The excised sensitized frog heart is markedly affected on contact with the specific sensitizing substance and this reaction seems to resemble light peripheral parasympathetic stimulation. It was shown that the muscle cells still respond to direct cellular stimulation. Excised smooth muscle from the alimentary tract of the frog did not exhibit the Schultz-Dale phenomenon and it is suggested that this may be explained by the fact that peripheral parasympathetic stimulation in this case does not produce contraction. These results would seem to offer further evidence that the precise site of the reaction is some portion of the neuro-muscular complex. It would seem that the characteristic features of anaphylactic intoxication in different animals depends not alone on the distribution of non-striated muscle but also on the character of the innervation of this muscle.