In practical disinfection it is a good plan always to _proceed as though spores were present_ even if the organism is known. Hence use an _abundance of the agent_ and _apply it as long as practicable_. Also it is best to secure the _chemical substances used as such_ and _not depend on patented mixtures purporting to contain them_. As a rule the latter are _more expensive_ in _proportion to the results secured_. _Surgical instruments_ may be sterilized by boiling in water for fifteen minutes, provided they are clean, as they should be. If dried blood, pus, mucus, etc., are adherent, which should never be the case, they should be boiled one-half hour. The addition of sodium carbonate (0.5 to 1 per cent.) prevents rusting. Surgeons’ sterilizers are to be had at reasonable prices and are very convenient. Whether the instruments are boiled or subjected to streaming steam depends on whether the supporting tray is covered with water or not. The author finds it a good plan to keep the needles of hypodermic syringes in a small wire basket in an _oil bath_. The oil may be heated to 150° to 200° and the needles sterilized in a very few minutes. The oil also prevents rusting. _Rooms_, _offices_ and all spaces which may be readily made practically gas-tight are best disinfected by means of formaldehyde by any of the methods above described (Figs. 111 and 112). _Stables_ and _Barnyards_ (Mohler): “A preliminary cleaning up of all litter is advisable together with the scraping of the floor, mangers and walls of the stable with hoes and the removal of all dust and filth. All this material should be burned since it probably contains the infective agent. Heat may be applied to the surfaces, including barnyard, by means of a ‘cyclone oil burner.’ When such burning is impracticable, the walls may be disinfected with one of the following: 1. Whitewash 1 gallon + chloride of lime 6 ounces. 2. Whitewash 1 gallon + crude carbolic acid 7 ounces. 3. Whitewash 1 gallon + formalin 4 ounces. The same may be applied with brushes or, more rapidly, sprayed on with a pump; the surface soil of the yard and surroundings should be removed to a depth of 5 or 6 inches, placed in a heap and thoroughly mixed with quicklime. The fresh surface of soil thus exposed may be sprinkled with a solution of a chemical disinfectant as above described. [Illustration: FIG. 111.--Formaldehyde generator used in city work for room disinfection.] [Illustration: FIG. 112.--Government formaldehyde generator.]