In order to elucidate still further the essential mechanism of the hematopoietic actions of polysaccharides extracted from the bone marrow, by Krawkow-Pissemiski's method the author studies the actions of these substances on the blood vessels of the ear lobes cut off from adult rabbits, and obtained the following results: 1) The polysaccharides extracted from the bone marrow act slightly dilatatively on the peripheral blood vessels of adult rabbits. 2) These substances seem to act antagonistically against the contracting actions of adrenalin and acetylcholine. 3) These substances seem to act cooperatively or as invigoratingly in conjunction with dilatative actions of atropine. 4) Ergotamine exerts almost no influence on the action of these substances. 5) These substances act strikingly antagonistically on the contraction by a blood vessel poison, barium chloride. From theses results it is construed that the mechanism of dilatation of blood vessels by these substances is the action to the vascular muscles, and that it possesses a parasympathetic nerve action on the vasomator and in addition, sympathetic nerve action though slight.