Thessalus, notwithstanding his declaration that medicine might readily be taught in six months, wrote a larger number of treatises on professional topics than any student of medicine could possibly read and digest in the course of two or three years. They filled several large volumes, but not one of them is known to exist to-day. He wrote at great length, as we are assured, on the subject of surgery, a subject in which he took an active interest. He taught that ulcers, no matter in what part of the body they may be located, require the same kind of treatment. If an ulcer is excavated, it is necessary to bring about a filling-up of the excavation; if its surface is on a level with the surrounding skin, the aim should be to make it cicatrize; if the growth of new tissue is excessive, the redundant portion should be destroyed by burning with caustic; and, finally, if the ulcer is of recent development and bleeds readily, the attempt should be made, by approximating the edges, to effect an immediate healing. In the treatment of chronic ulcers which show little or no disposition to heal, and which, when they do finally heal, are very prone to break open afresh, Thessalus urges the great importance of ascertaining, if possible, the cause or causes of this behavior. If it be found that the trouble is due to some weakness or abnormal predisposition of the part in which the ulcer is located, or that the condition of the entire body is probably the real cause of the trouble, he recommends the employment of “metasyncritic remedies”--that is, remedial measures which effect a marked change in the individual’s vital processes throughout the body, and also such as exert an alterative effect upon the ulcer itself. Among the measures of the first class he enumerates the following: Various forms of physical exercise; alternately increasing and diminishing the amount of nourishment taken; and perhaps the taking of an emetic at the very commencement of the treatment. As to the second class of measures--those needed to bring about a change in the ulcer itself--he makes the following recommendations: Remove from the diseased tissues as much as will restore the parts, as nearly as possible, to the condition of a healthy wound, and then adopt the treatment suited for the latter condition. In cases in which the ulcer heals and then subsequently breaks open again, it will sometimes be found beneficial to apply in the neighborhood a plaster containing an irritating substance like mustard, the effect of which is often to change the disposition of the parts. In actual practice he recommends that the local measures should be employed first, and then, if they fail to accomplish the desired purpose, the physician should have recourse to those enumerated in the first class--the strictly metasyncritic remedies.