1. Four mature dogs, weighing 10 to 12 kg, were anesthetized with "Zyclopan" and fractional aspiration of the gastric juice was performed through Levine's tube. On the other hand, secretion from the pouch which was previously prepared on the stomach of 30 dogs in Wedge or Heidenhain's method was collected at every 10 or 20 minutes. When the profuse secretion started about 1 hour later, 10 % cancer extract was injected intravenously into the leg vein of the dog in a dose of 1 cc of the extract per kg weight of the dog. The aspiration was continued for more three hours after the injection of the cancer extract in all cases. Volume of the specimen and its peptic activity were measured. 2. As a result of intravenous injection of cancer extract, the gastric pouch secretion decreased moderately and its peptic activity was depressed gradually. In most instances, peptic activity showed the maximum depression between 40 and 60 minutes after the injection, followed by gradual increase, and finally 3 hours after recovered to almost same level as at the beginning. The depression of gastric pouch secretion and its peptic activity after injection of the cancer extract, was more intensive and continued for longer time of period, compared to the cases injected with the extract of stomach wall. 3. These findings may partially depend upon the sudden change of the balance between water and electrolyte in blood, but the functional disturbance of gastric secretion cell by the cancer extract can be considered. 4. The experiment in vitro revealed the depressing action of cancer extract on peptic activity.