Using pieces of the mesenterium of rat the fragmentation of mast cells by drugs was examined quantitatively. In this experiment a modified technique of Norton's (1954), designed to keep fragmentation by artefact at minimum, was employed. The concentration-action curves of compound 48/80 and saponine in Ringer-Locke solution and the fragmentation curve of serial dilution of Ringer-Locke solution alone, all proved to be of sigmoid type. In these instances the fragmentation of mast cells was diminished on the acidic side between pH 5.2 and 8.5. Neoantergan inhibited the fragmentation of mast cells by compound 48/80, but it did not inhibit the fragmentation by saponine and hypotonicity. Cholesterol suppressed only the action of saponine. Diluting of Ringer-Locke solution strengthened additively the fragmentation of mast calls by 48/80. Of the several drugs tested only tannic aeid prevented the aetion of 48/80.
With this preparation a strong fragmentation aetion on mast cells could be recognized in some surface aetive subtances such as bile salts and chlorooetylresoreinol, but the action of sinomenine, D-tubocurarine and lycorine, that possess a strong in vivo action, was relatively weak. Hyaluronidase and trypsin did not show such an action.