(4) Mercuric chlorid, or corrosive sublimate, is a powerful disinfectant, but it is likewise very poisonous; hence its uses are limited. Cattle are especially susceptible to its action and caution must be used in its application. A solution of one-tenth of 1 per cent is usually sufficient (1 ounce to 8 gallons of water). It should not be placed in wooden pails, which would form the tannate of mercury, a weak antiseptic; nor, owing to its corrosive action, should expensive metal pails be used. Agate vessels or tin pails are to be preferred. All solutions should be labeled "poison," and to avoid accidents none should be kept on hand.
(5) Formalin and formaldehyde gas have been found very efficacious as sanitary agents. Formalin is the commercial name for the 40 per cent solution of formaldehyde gas in water, and is one of the most powerful antiseptic and disinfectants that we possess. Solutions of this strength are manufactured by different commercial houses and sold by the drug trade under the name of "formalose" and "formal." In this connection it should be mentioned that while the 40 per cent solution of formaldehyde gas and formalin are exactly the same thing, the former can be purchased at 33-1/3 to 64 per cent less than the latter. Formalin, diluted with water in the proportion of 1 pint to 30 parts of water, or 4 ounces to each gallon of water, may be applied, and it may thus be used as a wash or as a spray on all paints, metals, and woodwork, as well as on clothing and other fabrics, without injuring them. It may also be applied to floors, walls, and woodwork in whitewash by mixing 1 part to 30 parts of limewash, or 4 ounces to each gallon of limewash. Formalin has the appearance of water and in the strong solution is poisonous, but when diluted as recommended above it is not dangerous. The fumes given off by it, however, are very disagreeable and irritating to the eyes and nasal mucous membranes. One and one-half ounces of formalin added to 1 gallon of water is a valuable agent for the disinfection of the skin or septic wounds, but is somewhat painful and irritating to raw surfaces.
Formaldehyde is a gas which is soluble in 2½ parts of water (40 parts of formaldehyde gas to 100 parts of water); this solution constitutes the formalin of commerce. The use of formaldehyde gas is in most cases impracticable for stable disinfection. In case the stable is not too large and can be made almost air-tight the generation of formaldehyde gas, after removing all the animals, will be found very serviceable. It penetrates all parts of the stable—the walls, crevices, floors, ceiling—and is probably the best fumigating disinfectant that we have.
Probably one of the most simple and practical methods of liberating this gas is by means of the chemical reaction which takes place when formalin is poured upon permanganate of potassium. For each 1,000 cubic feet of air space, 16-2/3 ounces of crystallized or powdered permanganate of potassium is placed in a wide-surfaced pan; 20 ounces of formalin is then poured upon it, and the stable immediately closed for a period of 12 hours or longer. This method is efficient only when it is possible to seal tightly the place to be disinfected, and should be used only by experienced persons.
(6) Some coal-tar products are cheap, effective, and easily applied disinfectants, their action being due to the carbolic acid and creosote in their composition. They may be used in 3 to 5 per cent solution. As a rule they form a milky solution in water.
(7) Compound solution of cresol (liquor cresolis compositus), now recognized as an official preparation, is composed of equal parts of cresol and linseed-oil-potash soap. The mixture is a thick, dark, amber-colored fluid which mixes readily with water in all proportions to form a clear, soap solution. It is an efficient disinfectant in a 3 or 4 per cent solution, and in this strength it may be applied in the same manner as a 5 per cent solution of carbolic acid.
When it is desired to apply one of these above-mentioned agents to the stable or barnyard, a preliminary cleaning up of all débris and litter is advisable, together with the scraping of the floor, mangers, and walls of the stable with hoes; also the removal of all dust and filth. This should be followed by the burning of all such accumulations, inasmuch as this material likewise contains the infectious principle and is best destroyed by heat. Heat may be applied to the surface of the affected pen, byre, or barnyard by means of a cyclone burner, which consists of a tank, pump, hose, and cyclone nozzle for spraying with paraffin (gas oil). The latter is ejected in the form of spray, which when ignited gives a very hot and effective flame to be applied to the infected ground. Where such burning is impracticable the surface soil of the yard and surroundings should be removed to a depth of 5 or 6 inches and then placed in a heap and thoroughly mixed with air-slaked lime. The fresh surface of the soil thus exposed may then be sprinkled with the disinfectant.
In addition to these artificial substances there are several natural sanitary agents of great importance as destroyers of virus. These are cleanliness, ventilation, drying, and sunshine. All virus, excepting such as may live in the soil, is killed sooner or later by drying and sunshine, and the importance of these factors in the daily life of animals need not be insisted on here. Finally, all sanitary measures which contribute to the healthfulness of animal surroundings are directly or indirectly inimical to disease germs, and all carelessness in the keeping of animals may be regarded as an ally of these destructive organisms.