=Tuberculin.=--Finally the treatment of tuberculosis cannot be dismissed without a reference to the glycerin extract made from a filtered culture of the tubercle bacillus, containing the peculiar toxalbumin first prepared by Koch, forever associated with his name, and first given to the world in 1890, when its announcement created a furore and aroused hopes that have never been completely realized. Yet in spite of disappointments which have often followed its use, it is a remedy of great value when judiciously used in selected cases. The diagnostic value of the material should also not be forgotten, as by its use one may possibly decide in doubtful cases as between tuberculous or some other disease. The best preparation for use today is that made by Koch’s new process, by which the possibility of the presence of microörganisms is eliminated. It contains those constituents of the bacilli which are insoluble in glycerin, and which have distinct immunizing power. On the market it is known as _tuberculin rest_, indicated simply as T. R. The initial dose is ¹⁄₅₀₀ Mg., to be increased with each injection. Its effect, _e. g._, on lupus, is very marked. CHAPTER X. SYPHILIS. The younger generation, when studying the subject of syphilis, should be referred back one hundred years or more to the time when the opinions held by John Hunter generally prevailed--when venereal diseases were grouped under one heading, and considered to be but three manifestations of the same morbid condition. It took years for the profession to break away from this mistaken teaching, and a generation had passed before gonorrhea was separated from the others. This left chancroid and syphilis still more or less confused in the minds of many, and until the middle of the previous century they were considered as different types of the same disease by some of the most experienced observers. Thus it happened that those who made a special study of this subject were grouped into two classes, the _unicists_ and the _dualists_, according as they held to the unity or duality of syphilis and chancroid. It was a question of importance, and differences of opinions led to bitter antagonisms. Its importance inhered in this: either all venereal sores were to be subjected to constitutional treatment, or else differences in treatment were to be made according to the local or constitutional nature of the malady. Men sacrificed their own health, even their own lives, in their willingness to make experiments upon themselves, and auto-inoculability was proved by one observer through some 1700 inoculations produced upon his own body. Such devotion to medical science has been rarely eclipsed. In the latter half of the eighteenth century came clearer distinctions, and toward its close there were none who ranked as authorities who held to the old view of the unity of these diseases.