1st. That characterized by its circular form, its excavated surface covered by a layer of tenacious and adherent matter, and its hard cartilaginous base and margin. 2d. Another form of chancre, unaccompanied by induration, but with a very high margin, appearing often on the outside of the prepuce, and seldom existing alone, called, from the preceding description, the “superficial chancre, with raised edges.” These kinds of ulcers are sometimes very tedious, neither getting better nor worse, but resisting every plan of treatment for their removal. I have known instances where they have existed for several months. 3d. The phagedenic chancre, a “corroding ulcer without granulations,” and distinguished by its circumference being of a livid red color. This is the kind of chancre that is invariably rendered worse by mercury: indeed, cases have occurred where, from the injudicious administration of that medicine, the whole of the penis has been destroyed. 4th. A most formidable kind of chancre, denominated the sloughing ulcer. It first appears as a black spot, which spreads and becomes detached, leaving a deepened and unhealthy looking surface. The sore is very painful, and encircled with a dark purple areola. If neglected, or improperly treated, the process of mortification goes on until all the parts of generation are destroyed. The last-named chancre is more often the consequence of neglect on the part of the patient, than the natural progress of the disease. Now the usual method adopted by surgeons to remove chancres, has been to excise them, or to apply caustic; the latter is the plan I adopt, and would recommend; but all chancres are not to be treated alike, some requiring antiphlogistic remedies, others soothing, others stimulant. Some practitioners rely entirely upon constitutional remedies. On the first appearance of a chancre, I would enjoin an alteration in the diet, regulating it according to the strength of the patient. Abstemiousness should be the motto, avoiding extremes, however, lest debility should be induced. Quietude and rest, in the recumbent position, are two essential adjuncts in the treatment of primary syphilis throughout. With respect to the treatment of the ulcer, characterized by its circular form, excavated surface, and hardened base, as detailed, the plan I almost invariably adopt is, immediately on its appearance, at least as soon as the pimple has broken or desquamated, to smear it with a hair pencil filled with the solution of caustic, sometimes twice, at least once a day (see Form 27), and to keep it frequently washed in the daytime with a lotion of the chloride of soda (see Form 28), or the black, red, or blue wash (see Forms 29, 30, 31).