“…The mast cells are especially important in this respect. Specifically sensitized mast cells are degranulated by the allergic reaction, and histamine, bradykinin, and other transmitter substances are liberated (Graham et al, 1955;Katz and Cohen, 1941;Keller, 1966;Middleton, 1959). Slow-reacting substance A (SRS-A) is among the substances that are liberated in sensitized lung tissues by allergic reactions, but it is uncertain whether or not it origin- (1) spasm of smooth muscle, (2) oedema of mucosa, (3) increased secretion of viscidfluid, and (4) forced expiration to compensate for combination of factors 1, 2, and 3, causing increased external pressure on bronchi and bronchioles.…”