responding with the pressure as indicated by a steam guage. At 20 lbs. pressure the temperature is about 230 deg, Fahr. (105 deg. C.); at 25 lbs. it is about 240 deg. Fahr; at 30 lbs. it is 250 deg. Fahr. Moist heat at the lowest temperature named destroys the moist resistant spores in twenty minutes; with a temperature of 240 deg. Fahr. it is effective almost immediately. (1).

3. Boiling.-In the absence of spores, bacteria are quickly killed at a temperature considerably below the boiling point of water, and it is safe to say that boiling for half an hour will destroy all known disease germs, including the spores of anthrax, which have less resisting power than the spores of certain harmless and widely distributed bacilli, which have been found to resist boiling for several hours.

4. Chloride of Lime-(Chlorinated lime, bleaching powder).— This is one of the cheapest and most efficient of disinfectants. It should be packed in air-tight and moisture-proof receptacles, -glass is preferrable,-and should contain at least 25 per cent. of available chlorine. (2) It should be used in solution, which had better be made as required. An insoluble residue will be left which may be removed by filtration or decantation. This, however, is not at all necessary. Chlorinated lime owes its disinfecting power to the presence of the hypo-chlorite of lime, a salt which is freely soluble in water, and which is quickly decomposed by contact with organic matter. Germs of all kinds, including the most resistant spores, are destroyed by this solution, but it must be remembered that the disinfectant itself is quickly decomposed and destroyed by contact with organic matter, and that if this is present in excess, disinfection may not be accomplished, especially when the germs are imbedded in masses of material which are left after the hypo-chlorite of lime has all been exhausted in this solution,

5. Liquor soda chlorinatae (Larbarraque's solution).

This is a solution of hypo chlorite of soda. Its value as a disinfectant corresponds with that of solutions of the hypo-chlorite of lime of the same strength. The preparations in the market vary greatly in value, and some of those tested by the committee on disinfectants (3) were found to be practically without value. This is due to the fact that the solution does not keep well. For this reason, and on the score of economy, a solution of chloride of lime will be preferable for most purposes. Labarraque's solution is, however, a more pleasant preparation for bathing the surface of the body, and both as a deodorant and a disinfectant will be found useful in the sick room. It should contain at least three per cent. of available chlorine.

6. Mercuric Chloride (bichloride of mercury, corrosive sublimate). This salt is well known as a deadly poison, which has

(1). See preliminary report of committee on disinfectants in the Medical News, Philadelphia, Mar. 14, 1885, p. 284.

(2). The test for available chlorine is given in preliminary report No. 11 of the Committee on Disinfectants, 1. c., Jan. 7, p. 148.

(3) 1; c. p. 69.

long been used in domestic practice as a "bug poison." Recent researches show that it has germacide powers of the first order, and it is consequently a disinfectant which may be recommended for certain purposes, due regard being had to its poisonous nature, and to the fact that it is decomposed by contact with lead, tin, or copper, and that lead pipes are soon rendered brittle and worthless by passing through them solutions of mercuric chloride. Its potency in dilute solutions (1:500 to 1:4000) makes it comparatively cheap (1), and the danger of accidental poisoning from such dilute solutions is not very great. The concentrated solutions should be colored as a precaution against accident, for they have neither color nor odor to reveal their deadly nature.

A standard solution which contains four ounces to the gallon of water is of convenient strength for a concentrated solution, to be issued by manufacturers or health authorities in properly labelled bottles. This may be colored with permanganate of potash (2), or with indigo, or with aniline blue. Inasmuch as standard solution number two of the committee on disinfectants is colored with a permanganate, it would perhaps be better to give this solution a blue color. The writer would suggest the following formula, in which another poisonous metallic salt contained in our list is combined with the mercuric chloride:

It must be remembered, in using this and other disinfecting solu tions, that the condition relating to time of exposure to the action of the disinfecting agent is an important one. The experimental evidence (3) relating to the germacide power of mercuric chloride shows that the time of exposure being two hours, this salt may be safely recommended for the destruction of spore-containing infectious material in the proportion of 1: 1000, and of pathogenic organism in the absence of spores in the proportion of 1: 4000, or even less, provided that the micro-organism to be destroyed are fairly exposed to its action. The fact that the mercuric chloride combines with and coagulates albuminous material interferes to some extent with its value as a disinfectant, and will be kept in view in the recommendations to be made hereafter relating to the practical use of this agent. Mercuric chloride is an efficient antiseptic in the proportion of 1: 15000, and it exercises a restraining influence upon the development of the spores of the anthrax bacillus, when present in culture solutions, in the proportion of 1:300,000, and even less.

Dry Heat.-Dry heat is only to be recommended for the disinfection of such articles as would be injured by exposure, or to a disinfecting solution. A properly constructed disinfection cham

(1). It costs about 50 cents per pound by the quantity.

(2). Ten grains to the gallon is sufficient.

(3). The Medical News, Feb. 21, p. 205.

ber or "oven" is absolutely essential, if dry heat is to be used. The experimental evidence on record (1) shows that the destruction of spores requires a temperature which would injure woolen fabrics (140 deg. C. for three hours). In the absence of spores, however, articles which are freely exposed for two hours to a temperature of 110 deg. C. (230 deg. Fahr.) may with safety be considered disinfected. In practice it will be necessary to remem. ber that the penetrating power of dry heat is very slight, and that packages, bundles, or even articles loosely thrown one upon another, cannot be disinfected in this way.

8.-Sulphur dioxide (sulphurous acid gas). Fumigation with buring sulphur has long been a favorite method of disinfection. The experience of sanitarians is in favor of its use in yellow fever, small-pox, scarlet fever, diptheria, and other diseases in which there is reason to believe that the infectious material does not contain spores. The experimental evidence on record (2) shows that under certain conditions it is effective for the destruction of micro-organisms in the absence of spores, but that it is quite impotent for the destruction of these reproductive elements. The presence of moisture adds greatly to the disinfecting power of this agent. It is freely soluble in water, one volume dissolving fifty volumes of the gas. It is therefore evident that a saturated aqueous solution is fifty times as strong as the pure gas-anhydrous. In acqueous solution, in the proportion of 1:2000 by weight, sulphur dioxide kills micrococci in two hours' time. (3) In a gas-tight receptacle it destroys the infecting power of vaccine virus dried upon ivory points, when present in the proportion of one volume per cent., the time of exposure being six hours. (4) The same proportion destroys anthrax bacilli, without spores, from the spleen of an animal recently dead, dried upon silk threads, in thirty minutes (Koch). These facts show that sulphur dioxide is a valuable disinfectant; but the conditions of successful disinfection, as established by the experimental evidence, are, that the material to be disinfected shall be freely exposed to its action for a considerable time, in a receptacle which does not permit the gas to escape. It must be remembered that disinfection of a thin layer of vaccine virus upon an ivory point, or of anthrax blood upon a silk thread, exposed in a gastight receptacle, cannot be taken as evidence that thicker layers of infectious material, attached to the surface of clothing and bedding, or enclosed in folded blankets, bundles of clothing, mattresses, etc., can be disinfected by the same amount of sulphur dioxide generated in, a room which is not gas-tight. It has been shown, by carefully conducted experiments (5) that the escape of sulphurous acid gas from a bed chamber or hospital

(1) See Medical News, March 11, p. 233.

(2) See Prelim. Rep. No. VII, the Medical News, March 28, p. 243.

(3) 1. c., p. 348.

(4) 1. c., p. 344. (5) 1. c., p. 347.

ward is very rapid, in spite of the usual precautions for stopping up crevices when such room is to be fumigated; the infectious material, enclosed in bundles or protected by folds of blankets, etc., may escape disinfection, after having been exposed for many hours in a tightly closed chamber containing ten volumes per cent. of this gas.

9. Carbolic Acid.--The disinfecting power of carbolic acid has been fixed by experiments upon vaccine virus, and upon various pathogenic organisms. A saturated aqueous solution cannot, however, be relied upon for the destruction of spores; but in the absence of spores it is fatal to micro-organisms in the proportion of two per cent., the time of exposure being two hours. Indeed, less than one per cent. is fatal o several of the species of pathogenic micrococci which have served as test organism in the numerous experiments which have been made with this agent. (1). Upon the recommendation of the famous Dr. Koch, the discoverer of the cholera bacillus, the Committee on Disinfectants, of the International Sanitary Conference of Rome, (1885), has given this agent the first place for disinfected soiled clothing, excreta, etc., in cholera. For excreta it is to be used in five per cent. so lution, and for clothing, etc., in two per cent. solution. The experimental evidence upon record indicates that it may be relied upon in this proportion.

10. Sulphate of Copper.-This salt has been largely used as a disinfectant in France, and recent experiments show that in the proportion of one per cent. it is a reliable agent for the destruction of micro organisms in the absence of spores. It is much below mercuric chloride in germacide power, but is a better deodo rant--not a etter antiseptic-than the more poisonous salt. When we take into account its efficiency, it is comparatively cheap, and is to be recommended for certain purposes. It may be combined with the more potent germacide, mercuric chloride, in accordance with the formula already given.

11. Chloride of Zinc.-Solutions of chloride of zinc are largely used in this country and in Europe for disinfecting purposes. It is an excellent antiseptic and deodorant, and its power to destroy disease germs has been very much over-estimated. It may, however, be relied upon for the destruction of pathogenic organisms, in the absence of spores, in solutions which contain from five to ten per cent. of the salt.

GENERAL DIRECTIONS FOR DISINFECTION.

"In the sick room we have disease germs at an advantage, for we know where to find them, as well as how to kill them. Having this knowledge, not to apply it would be criminal negligence, for our efforts to restrict the extension of infectious diseases must depend largely upon the proper use of disinfectants in the sick room." (2).

(1). Prelim. Rep. of Com. on Disinfectants, No. VI., 1. c., p. 317,

(2). Prelim. Rep. of Com. on Disinfectants, of A. P, H. A.

Disinfection of Excreta, Etc.-The dejections of patients suffering from an infectious disease should be disinfected before they are thrown into a water closet or privy vault. This is especially important in cholera, typhoid fever, yellow fever, and other diseases in which there is evidence that the infectious agent is capable of self-multiplication, in suitable pabulum, external to the human body. Vomited matters, and the sputa of patients, with these and other infectious diseases, should also be promptly disinfected. This is especially important in cholera, diphtheria, scarlet fever, whooping cough, and tuberculosis. It seems advisable also, to treat the urine of patients sick with an infectious disease with a disinfecting solution.

For the disinfection of excreta, etc., in the sick room, a solution of chloride of lime is to be recommended. This is an excellent and prompt feodorant as well as a disinfectant. A quart of the standard solution (No. 1), recommended by the committee on disinfectants of the American Public Health Association, will suffice for an ordinary liquid discharge in cholera or typhoid fever; but for a copious discharge it will be prudent to use twice this quantity, and for solid fecal matter a stronger solution will be required. As chloride of lime is quite cheap, it will be the best to keep on the safe side, and to make the solution for the disinfection of excreta by dissolving eight ounces of chloride of lime in a gallon of water. This solution should be placed in the vessel before it receives the discharge. The material to be disinfected should be well mixed with the disinfecting solution by agitating the vessel, and from thirty minutes to an hour should be allowed. for the action of the disinfectant, before the contents are thrown into a water closet or privy-vault.

Standard Solution No. 2, of the committee on disinfectants, which contains two drachms of corresive sublimate and two drachms of perman-ganate of potash to the gallon of water, if freely used, one quart for each dejection, and left in contact with the material to be disinfected for at least four hours, is a reliable disinfectant for liquid discharges. The caution with reference to lead pipes must be remembered, and if this solution is used in the sick room or in hospital wards, it will be desirable to have receptacles of wood or earthen-ware for the disinfeced material, which may be carried away and emptied in a suitable locality once in twenty-four hours.

The blue solution heretofore suggested would also be suitable for use in the same way, and with the same precautions. It contains four ounces of corrosive sublimate aud a pound of sulphate of copper to the gallon of water. This concentrated solution should be diluted in the proportion of eight ounces to the gallon of water, and the diluted solution used as heretofore recommended, at least a quart for each dejection, and four hours' time. The disinfecting power of the copper salt adds to the value of this solution, and the bright blue color of the concentrated solution