Observations on the appearance of the tissue mast cells in the trachea, esophagus, stomach and skin were made after intramuscular injection of 0.3 cc of 5% Ipsilon, 0.1 cc of Adsone (5 mg/cc) and 0.06 cc of Vitamin K (10 mg/cc) per 100 gm of body weight respectively, on the central portion of the lateral side of the right thigh with 22 gauge needle with follow-ups at varying time intervals, using healthy albino-rats weighing 120-130 gm each. The results were as follows : 1) The tissue mast cells of the trachea, esophagus, stomach and skin decreased numerically to a minimum between 15 minutes to 45 minutes after the intramuscular injection of Ipsilon 0.3 cc per 100 gm of body weight and in 45 minutes after the intramuscular injection of Adsone 0.1 cc per 100 gm of body weight. After the injection of 0.06 cc of Vitamin K per 100 gm of body weight, the period to reach the minimum was 30 minutes. 2) The tissue mast cells of the various tissues increased numerically from the minimum to a maximum between 60 minutes to 120 minutes after the intramuscular injection of Ipsilon 0.3 cc per 100 gm of body weight and between 60 minutes to 150 minutes after the intramuscular injection of Adsone 0.1 cc per 100 gm of body weight. After the injection of 0.06 cc of Vitamin K per 100 gm of body weight, the period to reach the maximum was 90 minutes to 150 minutes. The time of recovery to the normal number of tissue mast cells was 12 hrs to 24 hrs in all 3 cases. 3) The decrease to a minimum of tissue mast cells was more extreme in the stomach, esophagus and trachea than in the skin with all of the hemostatics given. 4) The decrease to a minimum of tissue mast cells was greater in the following sequence of injection cases : Vitamin K, Adsone, Ipsilon. But there was no initial decrease in tissue mast cells of the skin in the case of Vitamin K injection. 5) The increase and decrease of the tissue mast cells was more rapid in both left and right skin cases than in the other tissues. 6) The increase to a maximum of tissue mast cells was greater in the internal organs than in the skin in the Adsone injection case ; on the other hand, in the Ipsilon injection case and the Vitamin K injection case it was greater in the skin than in the internal organs. 7) The numerical changes in the tissue mast cells of the contralateral side of the injection was almost the same as in the skin of the injected side. 8) In the morphology of the tissue mast cells after stimulation with various hemostatics, the percentage of the normal mast cells decreased and that of the degranulating form of the tissue mast cells increased with the decrease in the number of the tissue mast cells and afterwards, as the number of the mast cells increased, the percentage of the normal form increased and that of the degranulating form decreased, thus reaching the normal state. In general, the time of recovery to the normal state was delayed in the precentage of the normal form and degranulating form than in the number of tissue mast cells.