possible, and should be thoroughly purified before cholera comes into the neighborhood. Such cleansing and disin fection give the surest protection against pestilential epidemics.

It must be borne in mind, however, that although the so called disinfectants are very useful when properly applied, they are not, by any means, infallible preventives of disease.

Dr. Baxter,' from careful experiments, arrives at the following opposite conclusions in regard to disinfectants: No virulent liquid can be considered disinfected by carbolic acid unless it contains at least two per cent. by weight of the pure acid. When disinfectants are mixed with a liquid it is very important to be sure that they are thoroughly incorporated with it, and that no solid matters. capable of shielding contagion from immediate contact with its destroyer be overlooked. Aerial disinfection, as commonly practised in the sick-room, is either useless or positively objectionable, owing to the false sense of security it is calculated to produce. To make the air of a room smell strongly of carbolic acid by scattering carbolic powder about the floor, or of chlorine, by placing a tray of chloride of lime in a corner, is, so far as the destruction of specific contagion is concerned, an utterly futile proceeding. According to his views the practical result of these experiments goes to prove (1) that dry heat, when it can be applied, is probably the most effi cient of all disinfectants; (2) that the old plan of stopping up crevices and fumigating with sulphur and charcoal is more efficacious than any other proceeding with more. modern disinfectants; (3) that the use of carbolic vapor for disinfecting purposes should be abandoned, owing to the relative feebleness and uncertainty of its action.

Med. Times and Gazette, July 29, 1876.

Disinfectants in Common Use.

There are three important classes of disinfectants, each having specific uses as mentioned above. Some of these purifying agents accomplish only one object, others accomplish two or more objects; some may be advantageously combined; others are incompatible with each other, and must not be used together.

CLASS I. Positive Disinfectants that quickly destroy or completely restrain every contagious and infectious virus.

This class comprises the caustic acids, the acid salts of metals (soluble oxide salts), such as sulphate of iron, sulphate of zinc, etc.; carbolic and cresylic (impure carbolic) acids; which not only destroy every communicable virus of disease, but also prevent those kinds of fermentation and decay that aid in propagating epidemics. Frost destroys some infections, but preserves many others, while boiling or high steam heat destroys all contagious matter. It will be observed that no one of these agents, singly, is applicable to everything and every place that may require disinfection.

CLASS II. Antiseptics, comprising chemical agents that arrest or wholly prevent fermentation and decay.

This is a large class, and embraces carbolic and salicylic acids, and most of the agents of the first class; but not every antiseptic substance or gas (common salt or chlorine, for example) can absolutely prevent the fatal operation of epidemic infections.

CLASS III. Deodorants, absorbents, etc., comprising all the chemicals that deodorize or destroy putrid exhalations, or that absorb moisture and gases.

Charcoal, quicklime, and chlorine are good examples of this group.

Each of these three classes, and each disinfecting

agent, has its proper uses, and, as it is frequently important that these threefold means of disinfection should be applied at once to a given place or source of disease, the chemical properties of the several agents must be regarded. For example, it should be remembered that chlorine and the common alkaline compounds do not destroy the cholera infection; also, the fact that, if permanganate salts, carbolic acid, and chlorine be used together, or if the first two of them be mixed, they will simply destroy each other, and leave the infection undestroyed.

Volatile Disinfectants.-Carbolic acid on any surfaces. from which it will evaporate, or from which it may be vaporized by steam-heat, and the sulphurous acid fumes, are examples of disinfectants belonging both to the first and the second class. Bromine and nitrous acid have similar powers, but should be used only by medical officers.

Of the volatile deodorants in Class III., chlorine is the chief, and though useful for certain purposes in the other classes (I. and II.), if intensely concentrated, it is principally useful to destroy other gases and temporarily to arrest decay. It seems not to have power to destroy the infectious property of cholera, smallpox, and the cattle-plague, while the vapor, as well as the strong solution of carbolic acid, is believed by some to have the power of arresting the infectious activity of all of them. This view, however, as already stated, is not universally accepted.

How to Use Disinfectants.

Brief mention may now be made of the proper methods of using some of the most important of the above agents. The methods of disinfection which are here described

are preferred simply because they are effectual, safe, easily applied, and not expensive. They have been thoroughly tested, and are in accordance with the latest experience.

1. Quicklime.-To absorb moisture and putrid fluids, use fresh stone-lime finely broken; sprinkle it on the place to be dried, and in damp rooms place a number of plates or pans filled with the lime-powder; whitewash with pure lime, and not with kalsomine.

2. Charcoal Powder.-To absorb the putrid gases, the coal must be dry and fresh, and should be combined with lime; this compound is the calx-powder, as sold in the shops.

3. Chloride of Lime.-To give off chlorine, to destroy putrid effluvia, and to stop putrefaction, use it as lime is used; and if in cellars or close rooms the chlorine gas is wanted, pour strong vinegar or diluted sulphuric acid upon plates of chloride of lime occasionally, and add more of the chloride.

4. Sulphate of Iron (Copperas) and Carbolic Acid.-To disinfect necessaries, cesspools, drains, and sewers, and especially the vessels, grounds, or places in which the discharges from the sick with cholera and diarrhoeal diseases are evacuated, dissolve eight or ten pounds of sulphate of iron in five gallons of water, and add a pint of fluid carbolic acid (if it can be had); stir or agitate it. briskly, to make a complete solution. The uses of this solution in infectious diseases will be given hereafter.

5. Permanganate of Potassium.-To be used in disinfecting clothing and towels from patients sick with cholera, scarlatina, typhus or typhoid fevers, during the night, or when such articles cannot be instantly boiled: throw the soiled articles immediately into a tub of water in which there has been dissolved an ounce of the permanganate

salt to every three gallons of water. Boil the clothing as soon as it is removed from this colored solution, or boil them in it. The permanganate salts must not be used with the carbolic or coal-tar disinfectants. It is also best that chlorine and the chlorides should not be used at the same time or in contact with the latter class of substances.

6. Sulphate of Zinc.-The Weimar Conference recommended that sulphate of zinc should be used precisely as we use permanganate of potassium. The zinc solutions need to be much stronger than those of the permanganate: use at least two ounces of sulphate of zinc to one gallon of water. It must be remembered that, if any of these solutions are very strong, they would destroy clothing. At the best, they are but temporary substi tutes for disinfection by boiling.

7. Carbolic Acid (Fluid).-This may be diluted at the rate of from forty to one hundred parts of water to one of the fluid acid. Use this solution for the same purpose as copperas is used; also, to sprinkle upon any kind of garbage or decaying matter, and on foul surfaces, or in drains. When used to disinfect clothing, carbolic acid of a pure quality should be thoroughly mixed with its own quantity of strong vinegar, and next be dissolved in one hundred times its own quantity of water before the clothing is immersed in it. This mixture with vinegar insures such complete solution of the carbolic acid, that the clothing will not be burned by undissolved drops of acid when disinfected in the carbolic-water. This weak solution (one part to one hundred) will not injure common clothing, but the acid must be of good quality and free from tarry matter. The clothing, etc., will long retain the offensive odor of the acid, except in articles