The author injected intravenously the aqueous solution of tartaric acid of various concentrations each 0.5 cc per Kg, into rabbits and observed their effect on the circulatory system. Immediately after the injection of 10 % solution, the maximal blood pressure showed an average decrease of 5.7 %, the minimal blood pressure showed an average decrease of 10.1 % and the pulse curve amplitude decreased on the average 18.7 %. All these conditions returned to normal gradually. By the injection of 7.5 % solution, the pulse curve amplitude decreased in some measure and the pulse rate showed a slight increase immediately, but the blood pressure was almost unchanged. By the injection of 3.75 % solution, the maximal blood pressure increased on the average 6.4 % in 5〜15 minutes after the injection, the minimal Blood pressure showed a tendency towards an increase and the pulse, rate, increased in some degree immediately after the injection. Comparing the effect of tartaric acid upon the circulatory system above described with those of acetic acid and lactic acid on which the author has previously reported, we note the following : on the injection of 5/3 normal solution each of these acids similarly decreases the blood pressure and they differ only in the extent of this effect; on the injection of 1 normal solution tartaric acid has no effect on the blood pressure while acetic acid or lactic acid decreases the blood pressure ; and on the injection of 1/2 normal solution, in contrast to acetic acid and lactic acid which have no effect on the blood pressure, tartaric acid increases the blood pressure though in only a slight degree. I am much indebted to Prof. Toshikazu Mashimo, M. D. and Assist. Prof. Magoziro Maekaawa, M. D. for their kind guidance throughout this experiment.

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By intravenous injection of 0.5cc of 2% solution per Kg in rabbits, the maximal blood pressure showed the average descent of 19mm Hg (14.3%) immediately and then increased gradually to the normal value or higher. The minimal blood pressure changed almost parallel to the maximal blood pressure but to a slighter degree than the latter, and the average of the largest decrease was 8mm Hg (11.2%). The pulse curve amplitude decreased to some measure immediately after the injection then slowly recovered. The pulse rate showed a gradual decrease and about the time when the maximal blood pressure rose temporarily a little higher than its original value, reached the maximal decrease, an average decrease of 48 (19.8%), after which it was gradually restored. The changes which were caused by the injection of 1% solution were similar to those of the case above described excepting that the minimal blood pressure was almost unchanged. On the injection of 0.5% solution, the maximal blood pressure showed a tendency towards a slight decrease and the pulse curve amplitude decreased immediately to some extent, while the minimal blood pressure and the pulse rate showed no recognizable change. In a word, the blood pressure decreased immediately afrer the injection as many investigators have reported. But the increase of the blood pressure after its decrease was not so evident as they said and in contrast to their results the increase of the pulse rate immediately after the injection was not observed. The decreas of the minimal blood pressure was less than that of the maximal blood pressure in the absolute value and in the ratio of descent.

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