The iodides have not proved as successful as the mercurials; nevertheless, the combination is a popular one and sometimes of peculiar value. The potassium salt is the one generally used, as it is cheaper than the sodium compound. The latter, however, is less irritating and often more available. The lithium compound is ideal in some respects, but very expensive. The iodides may be given in large doses, to the extent of 30 Gm. or more (an ounce or more) in twenty-four hours. Large doses are sometimes necessary in the treatment of late syphilis of the nervous system. When it is necessary to put the patient rapidly under the influence of antispecific medication the combined use of these two drugs, as for example by mercurial inunction and the use of one of the iodides internally, will most speedily bring about the desired result. This result may be overreached, and sore mouth or other toxic manifestations may appear suddenly and unexpectedly. The mercuric salts are soluble in solutions of the iodides, and what is known as _mixed treatment_ is often employed. The salts may be combined in any desired preparation. Donovan’s solution is exceedingly valuable, the arsenic which it contains seeming to reinforce both the mercury and the iodine. The iodides produce eruptions or rashes which strongly simulate both syphilitic and non-syphilitic skin diseases, and confusion may arise from their use. In those who are sensitive to the iodides, and in whom catarrh of the mucous membranes is easily produced, it is best to begin with small doses, increasing them as circumstances may warrant. Some patients cannot take iodine in any form. When iodides irritate the stomach they should be given in essence of pepsin. Of the various vegetable remedies some are unreliable and of little value. Certain combinations can, however, be effected in some cases by which the value of the effective agents may be enhanced. _Zittmann’s decoction_ or _McDade’s formula_ will occasionally prove of service. In aggravated cases the former is believed to be the most effective of all methods of administering mercury. Tonics or any other medicines which may be called for in particular cases should be given judiciously. There is nothing in antisyphilitic treatment which precludes other treatment when needed. CHAPTER XI. CHANCROID OR VENEREAL ULCER. Since the time of John Hunter and his pupils, who confused the three totally different and so-called venereal diseases, pathologists have drawn a distinct line between _chancre_, which is simply the initial sore of syphilis, and _chancroid_ or _venereal ulcer_, which is a distinctly local lesion, often destructive, but never followed by constitutional disease, except of septicemic or pyemic type. It is usually found upon the _genitals_, about the foreskin, glans, and vulva, but may be met anywhere upon the body where infection has occurred. It is distinctly _auto-inoculable_, in which respect it differs from chancre.