While the principles established by Lord Lister have remained unchanged, the details in the treatment have been greatly simplified and made more efficient. For the information of the general reader, let me state a few facts. Bacteria are divided into two principal classes, in accordance with their form. One, known as “cocci,” from the Greek word coccus—“berry”—may be likened to billiard-balls. Some of these occur in bunches, which have been likened to bunches of grapes, and hence are called, again from a Greek term, “staphylococci.” Others are arranged in chains, like beads, and are called “streptococci.” These last are very much more virulent and dangerous than the staphylococci. Both of these produce pus or matter, and they are the most widely diffused and most common forms found in infected or suppurating wounds. One form is the cause of erysipelas. A second form, known as “bacilli,” may be likened to a lead-pencil. Among the various bacilli that have been discovered are those of tuberculosis, glanders, tetanus or lockjaw, etc. I omit many others found in medical disorders, as they do not concern this paper. How important these discoveries are may be seen by the following facts: Tuberculosis, next to that of suppuration, is, perhaps, the most widely extended infection to which man, as well as animals, is liable. We are all familiar with it in the form of “consumption,” but the non-medical reader is, perhaps, not aware of the fact that it affects not only the lungs, but also the bowels in consumption of the bowels; the bones, as is seen by every surgeon almost daily, and especially as the cause of the crooked backs seen in spine diseases; in the joints, as is seen in hip-joint disease, white swelling of the knee, ankle-joint disease, and similar disease of all the other large joints of the body; in the brain, in tubercular meningitis; in the abdominal cavity, in tubercular peritonitis; in the skin, in certain forms of ulceration, commonly called lupus; in the glands, as in the swollen glands, or “bunches,” in the neck, and endless other varieties which I need not name.