In the management of wounds and other surgical conditions it is necessary to eliminate various extraneous influences which tend to delay or arrest the natural process of repair. Of these, one of the most important is undue movement of the affected part. "The first and great requisite for the restoration of injured parts is _rest_," said John Hunter; and physiological and mechanical rest as the chief of natural therapeutic agents was the theme of John Hilton's classical work--_Rest and Pain_. In this connection it must be understood that "rest" implies more than the mere state of physical repose: all physiological as well as mechanical function must be prevented as far as is possible. For instance, the constituent bones of a joint affected with tuberculosis must be controlled by splints or other appliances so that no movement can take place between them, and the limb may not be used for any purpose; physiological rest may be secured to an inflamed colon by making an artificial anus in the cæcum; the activity of a diseased kidney may be diminished by regulating the quantity and quality of the fluids taken by the patient. Another source of interference with repair in wounds is _irritation_, either by mechanical agents such as rough, unsuitable dressings, bandages, or ill-fitting splints; or by chemical agents in the form of strong lotions or other applications. An _unhealthy or devitalised condition of the patient's tissues_ also hinders the reparative process. Bruised or lacerated skin heals less kindly than skin cut with a smooth, sharp instrument; and persistent venous congestion of a part, such as occurs, for example, in the leg when the veins are varicose, by preventing the access of healthy blood, tends to delay the healing of open wounds. The existence of grave constitutional disease, such as Bright's disease, diabetes, syphilis, scurvy, or alcoholism, also impedes healing. Infection by disease-producing micro-organisms or _pathogenic bacteria_ is, however, the most potent factor in disturbing the natural process of repair in wounds. SURGICAL BACTERIOLOGY The influence of micro-organisms in the causation of disease, and the rôle played by them in interfering with the natural process of repair, are so important that the science of applied bacteriology has now come to dominate every department of surgery, and it is from the standpoint of bacteriology that nearly all surgical questions have to be considered. The term _sepsis_ as now used in clinical surgery no longer retains its original meaning as synonymous with "putrefaction," but is employed to denote all conditions in which bacterial infection has taken place, and more particularly those in which pyogenic bacteria are present. In the same way the term _aseptic_ conveys the idea of freedom from all forms of bacteria, putrefactive or otherwise; and the term _antiseptic_ is used to denote a power of counteracting bacteria and their products.