A—Disinfection chamber. B—Partition wall separating infected from disinfected side. C—Door on disinfected side. D—Door on infected side. EE—Safety-locking bolt for securing door. FF—Stiffening rings on doors. G—Steam inlet from boiler. H—Steam separator for arresting water condensed in G. I—Valve controlling admission of steam to disinfecting chamber. K—Valve controlling admission of steam to coils. LM—Safety valves regulating steam pressure in chamber and coils respectively. NU—Pressure guages indicating steam pressure in chambers and coils respectively. OO—Objects after disinfection. P—Wheeled carriage and cradle for OO. Q—Hinged rails on which P runs. R—Exhaust pipe for steam and air on first admission. S—Thermometer showing rise of temperature (to control complete air evacuation). T—Valve for closing exhaust pipe R when air is completely evacuated. V—Sluice valve to cause sudden escape of steam. W—Cock to admit steam to ejector. X—Exhaust pipe fitted with ejector for escape of steam before and of air during drying. Y—Valve for admission of air for drying under suction of ejector. [In some types of this machine this valve is placed on the lower part of C.]

Steam when admitted into a disinfecting stove comes into contact with cold objects. If the steam is saturated, immediate condensation to 1 ∕ 1600 part of its original volume occurs. Its latent heat is at the same time evolved. The condensation causes enormous shrinkage in bulk. More steam is thus insucked into the partial vacuum produced, and this is repeated, until in every part of the mattress or other material undergoing disinfection equality of temperature is reached, when condensation of steam will cease, and disinfection is complete. If the steam is superheated and no condensation allowed, disinfection occurs by the relatively slow method occurring with dry heat. In practice at the early stage cooling causes some conversion of superheated into saturated steam, though subsequently the much slower process of disinfection by conduction of heat goes on. Hence superheated steam is a less efficient disinfecting agent than saturated steam.

Superheating is produced in disinfecting stores in two ways: (1) By a jacket around the stove, which is kept at about double the pressure and about 20° to 30° F. hotter than the interior of the stove; as in the older patterns of the Washington Lyon stove. (2) By having a jacket containing a solution of calcium chloride, which is heated by a furnace under the stove. This solution is kept at a constant strength by an automatic supply from a cistern. The temperature of the boiling water is thus raised without pressure to 225° F. This is the principle of Thresh’s stove. The object of superheating steam is to assist in rapidly drying materials; but this object can equally well be secured by periodically allowing the sudden escape of the steam confined under pressure, in pressure disinfectors. This last method is the best, as it can not only be utilised at the last stage of the disinfection for drying the articles; but at the earlier stage for sweeping the air out of the stove, and thus removing what, owing to its low conductivity for heat is one of the most serious obstacles to rapid and efficient disinfection.

In the above description it has been assumed that the steam, whether saturated or superheated, is confined, except when the exhaust is employed for drying purposes. Steam may also be employed as current steam. Current steam disinfectors are initially cheap, but more steam, and therefore more fuel, is required in their use; and unless pressure is used by impeding the escape of the steam a temperature of only 212° F. can be secured. Accepting Buchanan’s dictum, a stove supplying saturated steam under pressure at a temperature in the interior of the stove of 234° F. is to be preferred. This temperature with saturated steam destroys the spores of the most resistant known microbe (that of symptomatic anthrax). With superheated steam or hot air stoves on the same basis a temperature of 280° F. would be required, which is damaging to most textiles, except horsehair.

THE PRACTICE OF DISINFECTION.

The Management of the Sick-room and Patient requires careful and conscientious attention to detail. Certain details are given on page [319]. All unnecessary furniture, carpets, and hangings should be removed as soon as the nature of the illness is known; but unless these articles have been contained in close trunks or drawers, and not opened since before the onset of the illness, they must be disinfected. Food left over from the patient’s meals must be burnt, if solid, in the patient’s room; if liquid, emptied down the water-closet. Dry sweeping of the floors is to be avoided, only wet brushing or cloths being used. Volatile aerial disinfectants during the sickness are valueless.

The Treatment of Discharges from the Patient is the most important point in the management of infection. The stools should be received into a bed-pan containing a 5 per cent. solution of carbolic acid, a 3 per cent. solution of cresol or lysol, or a 5 per cent. solution of chloride of lime. Milk of lime (20 per cent. strength) is very reliable, when added like the preceding solutions in bulk equal to that of the stool to be disinfected. The urine and vomit, if any, should be treated in exactly the same way. The infection of enteric fever is often spread by undisinfected urine.

Discharges from the throat, nose and mouth of patients should be received into a solution of

The efficacy of the carbolic acid solution is increased by adding 2 oz. of NaCl, or 12-14 oz. of NaCl to each gallon. Pocket-handkerchiefs must be avoided, linen rags being employed instead, and placed at once in one of the above solutions or burnt.