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.
When infants at the breast suffer from eructations, sour vomiting, diarrhoea, light-colored papescent stools of bad odor, with crampy pains in the stomach, I have always found bismuth act well. In that form of diarrhoea which so readily affects children while being weaned, or during hot weather, or that which continues even after irritation has been removed, it is also of great service; from 1 to 5 gr. may be given several times daily to children of one year and under. Weller prescribed for children as much as 30 to 60 gr. of subnitrate every hour (interdicting milk during the treatment), with no other than good results (Deutsches Archiv, quoted American Journal, 1870).
The ulcerative diarrhoea and aphthous condition connected with phthisis is alleviated by full doses. Traube (one of the first to recommend the remedy in such cases) supports the view of its acting mainly as a mechanical protective, lessening local irritation, and consequently reflex peristalsis. We have already referred to a case in which the powder was found to line the whole tract, and it is evident that for such protective effect large doses are necessary. Dr. T. Thompson, who prescribed about 5 gr. of the subnitrate with magnesia and mucilage, and Monneret, who gave many drachms for a dose, are strong advocates of its advantages. The latter observer states that he had seen many persons who were apparently dying with tuberculous diarrhoea, restored for a time to comparative health ("Medico - Chirurgical Transactions," v., p. 31, and Bulletin, v., p. 47), but the results of others have not been so favorable. The persistent diarrhoea of enteric fever is sometimes well treated in the same manner.
When the motions are green, curdled, watery, and offensive, small doses (1/4 gr.) of gray powder act very well, especially when combined with bismuth, and the same powders are useful when curdled milk is frequently rejected from the stomach. When there is a simple diarrhoea, with whitish stools, Dr. Stephenson thinks that rhubarb and soda should replace the mercurial, for fear the latter should depress the strength (Edinburgh Medical Journal, 1871), and certainly, if it be continued unwisely, it may do so by irritating the mucous membrane, etc., but I have never seen ill-effects from the minute doses above recommended. For infantile watery diarrhoea 1/100 to 1/50 gr. of corrosive sublimate after each motion acts well (with due care). I think this is now a common experience; I have acted upon it for twenty-five years. In the acute diarrhoea and colic of adults, one of the best methods of treatment is the use of a pill of calomel (3 gr.) with opium (1 gr. or 1/2 gr.), followed, after three or four hours, by castor-oil or other laxatives.