This does not hold a place in the U. S. or British officinal catalogues; but, being an efficient remedy, under certain circumstances, requires notice. At ordinary temperatures it is gaseous, extremely fetid, and fatal to animals if respired. it is asserted to be irritant to the eyes; and M. Lunge states that he has seen his workmen suffer with ophthalmia from exposure to the gas, which has continued until he succeeded by a better ventilation in getting rid of the noxious agent. {Journ. de Pharm. et de Chim., 4e sér., iv. 234, Sept. 1866.) Water has considerable affinity for the gas, absorbing twice or three times its own bulk, and acquiring its offensive smell, with a disagreeable sulphurous taste.

Water saturated with the gas, when taken internally in moderate doses, produces the same alterative effects on the system as sulphur, increasing the various secretions, moderately exciting the circulation, and operating as an alterative in similar affections. indeed, the great probability is, that sulphur and sulphuretted hydrogen enter the system from the stomach and bowels in the same state of chemical combination, resembling in this respect chlorine and hydrochloric acid. When taken in great excess, however, similarity of action between it and sulphur ceases; for it is scarcely possible that the latter, no matter in what quantity it might be administered, could undergo in the stomach an amount of change, which would equalize its effects with those of sulphuretted hydrogen largely administered. I have before stated that this, when inhaled, in its gaseous form, is very poisonous. Air moderately contaminated with it causes nausea, headache, and general weakness; more strongly, convulsions; and still more strongly, great general depression, and loss of sensibility. it blackens the blood, and probably acts injuriously by depraving that fluid, as well as by a direct stupefying influence on the brain. Taken somewhat copiously into the stomach, in the liquid state, it produces gastric irritation, with nausea and vomiting; and, very largely swallowed, is said to act in the same manner as when inhaled, probably because its quantity is now beyond the protecting power of the alkaline matter, which it encounters in any attempt to enter the circulation. As a medicine, it has been given in the quantity of half a pint or a pint in twenty-four hours, in divided doses. One of the reasons why it is so much less poisonous swallowed than inhaled is, probably, as suggested by Dr. Cl. Bernard, that the gas is exhaled by the lungs almost as fast as it is received into the blood, and consequently that, as when absorbed into the radicles of the vena portae it must pass through the lungs before reaching the arterial circulation, it is prevented from being carried with the blood to the left side of the heart, and thence distributed over the system. Exactly opposite is the case with the poison inhaled, which passes directly to the left auricle. {Arch. Gén., Fev. 1857, p. 130.)

But sulphuretted hydrogen is interesting, in a therapeutic point of view, chiefly as the active constituent of natural sulphurous waters, and as being the main agent in the therapeutic operation of artificial sulphur baths.

Natural sulphurous waters have long been celebrated for their efficacy in numerous morbid conditions. They are used internally, and externally by local and general bathing. No doubt, much of their reputed effect is ascribable to the circumstances under which they are used at watering places; the comfort of relaxation, the pleasures and excitements of social intercourse, the influence perhaps of novelty, the fine scenery of the environs, pure air, exercise, etc.; but, all these abstracted, much is still left which can be ascribed only to the effects of the waters. Of the special application of this remedy, I shall treat under the following head; merely observing further, in this place, that our country abounds with natural sulphur waters, and often in situations where all the accessary advantages, above referred to, conjoin with their medicinal influence to act favourably on the health. Among them may be particularized the famous White, Salt, Bed, and Blue Sulphur Springs among the mountains of Virginia, the Blue Lick Springs in Kentucky, and those of Sharon and Avon in New York.

One important point in relation to the sulphurous waters is, that they should not be taken internally when the stomach is in a state of vascular irritation, or disposed to it; nor applied externally in a febrile condition of the system, or during the existence of acute inflammation of any one of the important organs. Caution even is required in cases of imperfect convalescence from these states, lest a return of them might be provoked.