A group of four calves with Pavlov pouches was used in a series of twelve-hour experiments on whole cow's milk and simple soybean milk, with the volume of gastric juice being determined at half-hour intervals throughout the twelve hours. The secretion on soybean milk was 21.41 percent greater during the first six hours of the twelve-hour period, but practically equal to the volume of secretion on whole cow's milk during the second six hours;A group of four calves with Pavlov pouches, two of which had rumen fistulae in addition, was run for a continuous experiment of fourteen days---seven days on whole cow's milk, and seven days on simple soybean milk, the volume of gastric juice being determined at half-hour intervals throughout the fourteen days---day and night, and a full feed of whole cow's milk or simple soybean milk being given each eight hours. The results of this experiment showed that the maximum half-hourly volumes of gastric juice secreted on soybean milk were higher than the maximum volumes on cow's milk but that the total volume of secretion for the 24-hour period was less when the soybean milk was fed;A group of five calves with Pavlov pouches was used in a series of sixteen-hour experiments in which fortified soybean milk was checked against skimmilk in determining gastric digestion, by measuring the volume of gastric juice secreted on the two diets. The volume of secretion on fortified soybean milk was 7.73 percent more than that on skimmilk during the first half of the sixteen-hour period and 3.28 percent greater during the second half of the period;A group of three calves with rumen fistulae was used to determine gastric acidity when fed fortified soybean milk and skimmilk. The fortified soybean milk was found to evoke a total acidity in the stomach, 6.62 percent higher than skimmed cow's milk, with the point of maximum total acidity, 12.58 percent higher than that for skimmed cow's milk. The free acidity of the soybean diet was lower by 15 percent than that for skimmed milk, with the point of maximum free acidity, 19.2 percent lower than that for skimmed milk. Free acid appeared the second hour after feeding, with skimmilk, and the fourth hour after feeding with fortified soybean milk. Samples taken up to sixteen hours after feeding contained soybean flour.