The original method of Lister was very elaborate, and included also the dissemination throughout the air of the operating-room{325} of a vapor of carbolic acid, which was disagreeable, sometimes almost fatal, to operators and bystanders alike,--its use being based upon the notion that the air was the substance most to be dreaded. The instruments were placed in strong antiseptic solutions, usually carbolic, which were pungent and irritating to the hands of all that came in contact with them. So thoroughly and ubiquitously were antiseptic materials employed that it was soon learned that they were of themselves rather injurious to the best interests of the patients upon whom they were employed. Their use, of course, was contingent upon the notion, then everywhere prevalent, that powerful substances must be used in order to counteract the activity of the much-dreaded germs. In the course of time, however, it was learned that the air was not so much to be dreaded as had been supposed, and that even if it came in contact with raw tissues infection did not certainly follow. It was found also that the antiseptic solutions which had been so freely used for irrigating or drenching the parts during an operation were by no means essential, and that tissues often healed better which had not been subjected to so much irritation. It was learned further that it was not necessary to impregnate dressings with these same solutions, providing, in the first place, they were carefully sterilized by the application of heat, which in time came to be used for the purpose of sterilizing everything not injuriously affected by it. In consequence, then, all dressing material, silk ligatures, instruments, nail-brushes, etc., were subjected to live steam or to boiling water for twenty minutes or more, which was demonstrated to be completely effective in the destruction of all organic or bacterial life. This, of itself, was a very great simplification of the antiseptic method. It was also demonstrated that the vital fluids of the animal body had of themselves great germicidal power, and that the strong antiseptic fluids previously used tended rather to impair{326} this power than to enhance it. Accordingly, fluids for irrigation came to be used only when there was some noxious material to be washed away. It was found that fresh wounds healed most kindly when least irritated by applications of any kind, providing only that nothing came in contact with them which could infect them. And, in this way, as well as by resort to simpler rather than complicated procedures, there was gradually substituted for the so-called _anti_septic method that which is now everywhere recognized, and always practiced, when possible,--i.e., the aseptic method. This simply means that it is very much better to exclude germs than to permit of their access and then try to kill them after they have lodged. The aseptic method is, therefore,