The release of histamine during anaphylaxis has been demonstrated in several species and various tissues, but it is well known that histamine alone cannot satisfactorily account for all the effects on smooth muscle observed during the anaphylactic reaction. The experiments presented in the present paper show that in addition to the release of histamine, the antigen-antibody reaction results in the formation of another smooth muscle-stimulating substance which causes a slow and long-lasting contraction of the guinea-pig ileum, and which is resistant to anti-histamine drugs.

The release of histamine during anaphylaxis has been demonstrated in several species and various tissues, but it is well known that histamine alone cannot satisfactorily account for all the effects on smooth muscle observed during the anaphylactic reaction. The experiments presented in the present paper show that in addition to the release of histamine, the antigen-antibody reaction results in the formation of another smooth muscle-stimulating substance which causes a slow and long-lasting contraction of the guinea-pig ileum, and which is resistant to anti-histamine drugs.