In secondary forms of this disorder, as in Periostitis, ulceration of the mouth and throat,--or in any of the late rashes, as Rupia,--Iodide of Potassium is the best remedy. Its efficacy in such cases was discovered by the late Dr. Williams. It may sometimes fail to effect a cure; but this failure is often due to the omission of Mercury in the treatment of the primary disease. It would seem as if it were not so much the real secondary syphilis, but a certain smouldering action of a part of the poison which has escaped the operation of Mercury, but has been modified by it, which is capable of being met and controlled by Iodide of Potassium. In cases where this remedy fails, I have found that a course of the Bichloride of Mercury, combined with Sarsaparilla or some bitter tonic, proves very beneficial. But the action of the Iodide on a case of Periostitis, and the rapid absorption that follows its exhibition, are sometimes fully as remarkable as the influence of Mercury over the primary disorder. Sarsaparilla is a very doubtful member of this order. It contains a soluble principle called Smilacine. It is thought by some to purify the blood, and also to have a kind of specific influence over it in old syphilitic cases. If it were so, we should have from the vegetable kingdom a distinct analogue to one of these mysterious mineral Catalytics. But it is so rarely given without being combined with some more powerful agent, that it is difficult to judge whether or not it may have any striking virtues of its own. The Antisyphilitics, particularly the insoluble compounds of Mercury, are frequently employed as local applications to sores and eruptions. When these have a syphilitic origin, the mercurial doubtless combats the local manifestation in the same way that it can counteract the general action in the blood. In other cases the Mercury may pass into the blood of the part, and, by exerting in its antiphlogistic operation, the result of which is to diminish its plasticity, may thus promote absorption. Mercurial ointment, if rubbed into the skin, becomes in part absorbed, and may thus produce salivation. ORD. III. ANTISCROFULICS. These are medicines which have the power of counteracting the poison of Scrofula in the blood. Common and pernicious as is this disease, there are not many Catalytic remedies which exert any marked control over it. When a strumous condition is chronic, and has firmly established itself--when it has descended through many generations of the same family,--it is very intractable and difficult to cure. Palliative and indirect remedies, aimed rather at the consequences than at the source of the disorder, are often adopted with benefit. Tonics, Chalybeates, Cod-liver oil, and cold bathing, are frequently of use in improving the condition of the system, when debilitated by the long continuance of strumous disorders. But the most important and direct remedies for Scrofula are to be found in Iodine and its compounds.