After making clear the influence of some sympathetic poisons upon the coagulative components, consequently, upon the blood coagulability, it was able to apprehend that the autonomic nerve system may have a close relation to the formation of each component, and also, having compared the action of other sympathetic poisons with those of adrenalin, it was brought to light that tyramin, when large doses are injected, acts upon the blood coagulation, quite dfferently from the case with adrenalin, and the action of tetrahydro-β-naphthylamin (β-T) manifests a still less analogous effect. 1) Adrenalin, when injected intravenously in small doses in a rabbit i.e. 0.001-0.01 mg per kg shortens the coagulation time to one-half or one-third of the former duration, iucreases fibrinogen and thrombin, and decreases antithrombin. By increasing of the dose, the shortening after small dose changes to a lengthening, which later is followed by a shortening after a medium dose as 0.01 mg, while after a large dose (i.e. 0.03-0.05 mg) comes to a lengthening only. As for coagulative components it decreases fibrinogen and thrombin, and increases antithrombin in these doses. The effects of adrenalin on the clotting time take no corresponding course with those on body temperature but consist with a part of those on the number of white blood corpuscles. Farther the addition of various amounts of adrenalin to the blood-plasma does not give any influence upon the clotting time. On the other hand there is a welldefined parallelism between both the curves of change in the amount of coagulative components, and the lengthening or shortening of the coagulation time. The action of adrenalin, therefore, seems principally due to the change of the quantity of coagulative elements in the blood. Secondly, from the cercumstances that the action of adrenalin in small doses on the coagulative components is reversed by the preliminary disposition of atropin (or yohimbin), I am led to a conclusion that adrenalin in small doses hastenes the coagulation by stimulating the accelerative fibres of the sympathic nerve, while in larger doses, retards it by irritating its inhibitory fibres. 2) Experimenting on a rabbit, tyramin given intravenously in small doses (i.e. 0.005-0.01 g) quickens the coagulation time of blood having no direct action on the blood with added tyramin. Fibrinogen and thrombin increases when small doses are injected, while fibrinogen decreases, and antithrombin increases with large doses. 3) By injecting β-T in large doses (i.e. 0.01-0.03 g) it retards the coagulation time, and decreases fibrinogen and thrombin, and increases antithrombin, but with small doses (i.e. 0.003-0.005 g) it hastenes, though the change of those coagulative components are similar but uncertain. 4) On the process of clotting, tyramin in large doses as well as β-T appear to be acted upon from some other unknown cause than by stimulating the sympathetic nerve, as adrenalin does.