This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The seeds are about 2 to 3 mm. long and 1 to 15 mm. wide, boat-shaped, pale greyish brown in colour, usually with a pinkish tinge; on the convex surface there is a small, elongated, brown spot; on the concave surface is the hilum covered with a thin, whitish membrane; when soaked in water the seed coat swells and the seeds become surrounded with a transparent, colourless mucilage free from taste and odour. One part of the seeds with twenty of water forms a thick, tasteless jelly.
1 Pharmacographia, p. 403.
-The chief constituent is the mucilage which is contained in the cells of the epidermis; it swells and dissolves when the seeds are immersed in water.
In dysentery and chronic diarrhoea; taken dry they absorb water in the intestine yielding a protective mucilage; they are also used as a poultice.
Psyllium seeds (flea seeds), the seeds of Plantago Psyllium, Linne, are similar but smaller, dark brown and shining; they are much used on the continent for diarrhoea.