吾人欲明瞭methyltryptamine 對循環系統之作用，使用大白鼠做實驗其結果如次: 1. Methyltryptamine 0.05mg/kg以上對血壓、心跳及呼吸運動均有顯著之作用。即給與Methyltryptamine 0.05mg/kg時有血壓下降之趨勢，給與0.1mg/kg之Methyltryptamine血壓即上升。當給與0.2mg/kg之Methyltryptamine時，血壓則先下降而後上昇，然後恢復原血壓值。除此外， 0.2mg/kg之Methyltryptamine則有呼吸運動隨血壓之升降而有促進及抑制之現象。 2. Tryptamine之藥理作用較Methyltryptamine更顯著。 3. Methyltryptamine對切斷頸部兩側交感迷走神經之大白老鼠，有更顯著之藥理作用。 Effects of N-monomethltrptamine (MT) , which was prepared from Abrus precatorius growing wild in the sourthern part of Taiwan, on carido-vascular system were studied as compared with tryptamine in Albino rats, and the following results were obtained. 1. The intravenons injection of 0.05mg/ kg or more dose of MT caused an immediate change in blood pressure. 2- The actions of tryptanline a blood pressure were similar to that of MT but its duration was much longer. 3. Pretreatment with cutting of the bilateral vagus and sympathetic nerve remarkaole alter the action of MT on blood pressure and respiratory effects.