Taylor thinks his own cases mentioned above throw doubt over this inference. But it must be remembered, that his patients had dined just before taking the poison. It is not improbable that the activity of oxide of arsenic is impaired by admixture with other insoluble powders. M. Bertrand, conceiving from some experiments on animals that he had found an antidote for arsenic in charcoal powder, took no less than five grains of the oxide mixed with that substance, and he did not suffer any injury, although his stomach was empty at the time, and he did not vomit.[597] But Orfila afterwards showed, that other insoluble powders, such as clay, have the same effect; that no such powder can be of any use if not introduced into the stomach till after the arsenic is swallowed; and that they appear to act solely by enveloping the arsenical powder and preventing it from touching the membrane of the alimentary canal.[598] Although M. Bertrand’s discovery will not supply the physician with an antidote, the medical jurist will not lose sight of the interesting fact, that, by certain mechanical admixtures, arsenic in moderate doses may be entirely deprived of its poisonous quality. A singular case of recovery from no less a dose than sixty grains, which happened in the case of an American physician, probably comes under the same head with the experiments of Bertrand,—a large quantity of powder of cinchona-bark having been swallowed along with the arsenic. In this case, however, the symptoms were severe for three days.[599] The tendency of habit to modify the action of arsenic is questionable. So far as authentic facts go, habit has no power of familiarizing the constitution to its use. One no doubt may hear now and then of mountebanks who swallow without injury entire scruples or drachms of arsenic, and vague accounts have reached me of patients who took unusually large doses for medicinal purposes. But as to facts of the former kind, it is clear that no importance can be attached to them; for it is impossible to know how much of the feat is genuine, and how much legerdemain. With respect to the latter facts, I have never been able to ascertain any precise instance of the kind; and so far as my own experience goes, the habit of taking arsenic in medicinal doses has quite an opposite effect from familiarizing the stomach to it.