RÉSUMÉ
Histological studies were carried out on the degranulation of mesenteric mast cells of albino rats in which excised pieces of rat mesentery were incubated in media containing morphine and meperidine hydrochloride. The following conclusions were obtained. 1. The experimental dose of 0.04mg./ml. of morphine hydrochloride in Tyrode solution for the incubated mesenteric pieces brought about the degranulation of mast cells. 2. The experimental dose of 0.04mg./ml. of meperidine hydrochloride in Tyrode solution for the incubation of the mesenteric pieces did not effect the cytological changes of the mast cells. 3. By the addition of metabolic inhibitor such as iodoacetic acid to the incubating medium the degranulation of the mast cells was remarkably inhibited for the group in which the incubation was carried out for 20 minutes. However, the inhibition of the degranulation of the mast cells due to the metabolic inhibitor was abolished after 30 minutes of incubation. Consequently the authors have demonstrated the effect of morphine hydrochloride in its ability to induce a degranulation of mesenteric mast cells in vitro.