Active Ingredients. - The properties of the root are believed to depend upon the presence of a volatile crystalline substance, called hemidesmine or hemidesmic acid. They are yielded to boiling water, but little is yet accurately known respecting their nature.

Physiological Action. - Upon this point likewise nothing is yet definitely known, except that the effects of the plant are generally diuretic.

Therapeutic Action. - The diuretic virtues of hemidesmus render it useful in certain diseases of the kidneys: also for some syphilitic skin diseases, and for indigestion, when it becomes serviceable after the manner of sarsaparilla, with which reputation it was brought to England by Dr. Ashburner, about the year 1830. In India, where the plant is common, the roots are largely employed as a substitute for sarsaparilla, acting also as a tonic and diaphoretic.1 In England, however, hemidesmus is principally employed as a flavoring agent. Lindley stated, in 1838, that much of it was then employed in London as a very fine kind of sarsaparilla, and that it was said to be quite as efficient a medicine as the best sarsaparilla of America. The roots of other species of hemidesmus are probably sometimes mixed with it, or substituted for it.

1Waring ("Manual of Practical Therapentics") quotes O'shaughnessy to this effect, and decidedly concurs with the view of the latter that hemidesmus resembles sarsaparilla, but is superior to it for the above-named purposes.

Preparations and Dose. - Syrupus Hemidesmi (B. Ph.), 3j. - ij. (5. - 10.).