Fig. 13.—Willy Meyer Sterilizer.
Fig. 14.—Wallace Sterilizer.
Wallace Sterilizer.—Its chief feature is the addition of a reservoir fitting with the separated sterilizer into the outer body. See [Fig. 14]. This reservoir automatically regulates the water and steam supply. It is filled with water and inserted into the compartment provided for and adjoining the sterilizer. Through an opening in the bottom the water is permitted to escape into the sterilizer until the bottom of the latter is covered to a depth of ⅛ inch. As the heat is applied from the alcohol lamp this film of water is rapidly converted into steam.
The dressings arranged in the large tray are placed in the sterilizer and the supply of steam is maintained through the constant and steady flow of water from the reservoir, which compensates the evaporation in the sterilizer. In about twenty minutes the formation of steam in the top of the reservoir exerts sufficient pressure to force all the boiling water from the reservoir into the sterilizer to the depth of about 1½ inches. The tray of instruments is now inserted and the process continued for another ten minutes. Much less heat is required with this apparatus than with those of ordinary type, while sterilization can be continued uninterruptedly for one and one half hours, if need be.
Sprague Sterilizer.—The most perfect sterilizer is that of the Sprague type, in which a dry chamber is surrounded by steam under pressure. The apparatus is shown in [Fig. 15].
Fig. 15.—Sprague Type of Sterilizer.
Its cylindrical chamber is surrounded by two heavy copper shells, the space between which is occupied by the water. This compartment is entirely shut off from the sterilizing chamber, and as the steam is generated, the inner, or sterilizing, chamber becomes heated to a degree nearly equal to that of the steam in the surrounding cylinder; this prevents any condensation of steam taking place in the dressings. By opening the lever-handled valve at the bottom of the sterilizer in the rear, and the valve to the right, on top of the sterilizer, and allowing them to remain open for a space of four or five minutes, a vacuum is formed in the sterilizing chamber. These two valves are then closed, the lower one first, and the steam from the outer cylinder is allowed to enter the chamber, by opening the left valve on top.