Cascara Sagrada is prepared in many ways, but the most favorable preparation for experiment is the dried extract. This is the dark yellow powder familiar in commerce. It is found that in shaking this powder in distilled water it is almost entirely insoluble. The result is a dirty yellow mixture, the filtrate from which gives an acid reaction. This suggested neutralizing the mixture or making it alkaline. A small amount of sodium bicarbonate was added, and the powder immediately went into solution, producing a clear dark brown fluid.[92] A similar result was obtained by adding sodium hydrate. It was found that ¹⁄₂ g. of the dried extract could be dissolved in 25 c.c. m/24 NaHCO_{3}. This solution in NaHCO_{3}, is practically neutral. If a few drops of dilute H_{2}SO_{4} be added a yellow precipitate at once appears giving a mixture or suspension similar to that originally obtained by adding the powder to distilled water. The addition of NaHCO_{3} will again produce the characteristic dark brown solution. The extract is much more readily soluble in a stronger solution of NaHCO_{3}. The dried extract is thus soluble only in a neutral or alkaline fluid. It is insoluble in distilled water on account of the free acid which is present in the powder. Cascara extract is readily soluble in the intestinal juice of a rabbit, a characteristic dark brown clear solution being obtained. On the other hand, it is insoluble in the gastric juice, and an alkaline solution added to the gastric juice is at once precipitated. It was found that the intravenous injection of 1 c.c. of a 2% solution of cascara extract in m/25 NaHCO_{3} produces within a minute very strong peristaltic movements in the intestine. A similar injection of the same amount of m/25 NaHCO_{3} alone produces no such result, though stronger solutions of NaHCO_{3} cause a slight increase in intestinal movements. It is therefore the cascara in solution which produces these strong contractions. A somewhat larger quantity of the cascara solution injected subcutaneously produces increased peristaltic activity after an interval of several minutes. If the cascara solution be applied directly to the serous surfaces of the intestine, very strong contractions and peristaltic movements result in 2 or 3 minutes. A solution of m/25 NaHCO_{3} alone produces very slight movements when applied in this way. These can, however, be readily distinguished from those produced by cascara. The latter are much more powerful, are slower in developing, and can be only partially inhibited by m/6 CaCl_{2}. The movements following the application of pure NaHCO_{3} solution, however, are weak, they appear almost immediately, and can be entirely suppressed by the application of m/6 CaCl_{2} solution.