These affect the liver and the glandular appendages of the mucous membrane, and increase the tonicity of the muscular layer of the intestine. They increase the proper secretion of the glands, and do not merely cause an outward diffusion from the vessels into the canal.

Hydragogue Purgatives act with great energy, and not only increase the glandular secretions, but cause a very abundant outward diffusion, so that the dejections which they produce are extremely watery. This group of purgatives also excite very rapid and violent peristaltic movements.