The principle underlying the resort to antiseptic methods is summed up in the expression, now so generally received,--the "germ-theory" of disease. It refers, in general, to the so-called zymotic, or infectious, diseases, whose manifestations are protean, which are all communicable by one means{317} or another, but which are not all necessarily contagious; some of which, being not at all amenable to surgical treatment, are regarded as "medical" diseases, while others, which occur mostly in connection with surgical cases, or which lead to conditions requiring surgical relief, are usually spoken of as "surgical" diseases. As excellent and only too common examples of these zymotic diseases may be mentioned tetanus, erysipelas, puerperal fever, typhoid fever, and those varied conditions which are generally grouped under the term "blood poisoning." Those which most concern the surgeon, and those in which most remarkable relief has been obtained are erysipelas and the various forms of blood poisoning. These, in their varied manifestations, have, until recently, been literally the terror of surgeons, and in military hospitals, for instance, have been the cause of more deaths than have ever resulted from wounds directly upon the battle-field. In civil hospitals, as well as in general and private practice, the mortality from these diseases was, until twenty-five years ago, simply frightful; while frequently, and over wide areas of territory, endemics and epidemics of puerperal fever would result in the death of almost every lying-in woman. In consequence of this terrible death-rate surgeons were afraid to operate, and certain classes of operations, especially those on the abdomen and joints, were never performed, except under most exacting circumstances. But few of the present generation can actually realize the completeness of the changes brought about by the adoption of the germ-theory, and the practical effect of its use as a working basis for combating disease. While no intelligent student at present denies that the infectious diseases--of which the above named are but a very few--are the result of the introduction into the body, from without, of minute living organisms, for the most part vegetable,--thus constituting them in reality, as they are often called, _parasitic_ diseases,--but few are so familiar with{318} the history of modern discovery as to appreciate the basis upon which it has been demonstrated. The proof of the germ origin of disease is the legitimate outcome of the discovery of the actual causes of fermentation and putrefaction.