This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Dr. H. Wood speaks of the sulphate of magnesia as the best aperient in enteritis and colitis, when one is required: (usually treatment by opium is to be preferred).
In true dysentery there is much evidence as to the value of the same salt, although it is not generally known. Trousseau called attention to it in 1826 (Archives Gen., v., xiv.), Giacomini recognized it ("Treatise on Materia Medica"), and Stille confirmed their observations: he gave about 60 gr., freely diluted, every two hours, with the result of at once diminishing tenesmus and bloody discharges, and inducing watery feculent stools: the treatment should be commenced early, and is best suited for sthenic cases: an occasional opiate at night may be given during the treatment. That the same method is equally available for chronic and debilitated cases is shown by the experience of Mr. Ford in Melbourne, when dysentery was for a long time epidemic and more severe in character than he had ever seen it in this country. Some of his patients (medical men and others) had suffered for many months, with only temporary relief from chalk mixture, laudanum, etc., when he gave them drachm doses of the sulphate, with 20 min. of sulphuric acid, every four hours, and a blue pill, with opium (1 gr.), at night. Mustard was applied over the abdomen, and farinaceous diet ordered. In the course of twenty-four to thirty-six hours, the dejections became feculent, with less blood, and in about nine days all irritation had usually subsided. Mr. Ford adopted this method on the hypothesis that excessive action prevailed in one part of the intestine (the colon), while the rest of it was inactive; and he hoped to "restore unity of action," and also to "eliminate morbid material." However this may be, he is able to report that, in seven years of extensive practice, he did not lose one case of dysentery in the adult (Australian Journal and Ranking's Abstract, i., 1859).