confine the germs of contagion to the sick-room by hanging at the door a sheet, wet with a chlorinated lime or a phenol solution.

Present knowledge shows that most contagion is direct,even the contagium of small-pox not being able to travel more than a few feet. However, "direct contagion" can occur at any distance, when clothing or other articles have become infected by contact with the secretions of the patient, and such contagium being swallowed, inhaled, or otherwise absorbed by an individual who is not immune may cause infection. It has been proved that most contagiums are transmitted by "carriers," who may harbor disease with immunity and impunity, and by "missed" cases, patients who have the disease but who are so slightly sick that their illness is not recognized. Also many diseases are acquired only by infection from an intermediate host, such as lice, fleas, mosquitoes, etc.

Some pathologic bacteria die very quickly when exposed to the air, and especially when exposed to the sun. The pathogenic bacteria that seem to be the shortest lived are the germs of influenza, cerebrospinal fever, gonorrhea, and probably the germ of anterior poliomyelitis. The contagium of whooping cough survives during a short period only, though the disease still progresses. Diphtheria bacilli, typhoid bacilli, and tubercle bacilli may survive in dust or other material for a considerable length of time; however, diphtheria and tuberculosis are probably rarely thus acquired, but generally by the more direct "droplet" method of transmission.

The germs of typhoid and paratyphoid fevers, of dysentery, of cholera, and perhaps other germs that cause diarrhea, are not air-borne, but are acquired by the contamination of some food or liquid that is taken into the stomach unsterilized. Typhus fever has been shown to be caused by the bites of infected lice, and bubonic plague by the bites of infected fleas.

Because ordinary colds, tonsillitis and influenza so rapidly spread, it was thought they were disseminated by the air, but it is now known that they are only spread by contact, although the air near the patient may become contaminated by coughing, sneezing, laughing, and even by loud talking, unless a handkerchief or other protection is used. Some inflammations of the

eye, and some contagious diseases of the skin are spread only by contact. Measles and scarlet fever are spread by secretions from the upper air passages, or perhaps from a suppurating ear, but not by the eruptions on the skin. Pneumonia also is acquired by close contact with the secretions of those who are ill with pneumonia or are carriers of pneumonia germs.

One of the aids to direct contact is the fly, which can carry in its mouth and on its feet the germs of contagion and deposit them on food or liquid, or on handkerchiefs, or in some way that direct contact may be caused, or it may deposit germs on the lips or face of the individual. In other words, the fly is a menace, especially where there is contagion; therefore the sickroom must be screened absolutely against flies.

Infected mosquitoes are the cause of malarial fever and of yellow fever. Certain types only of mosquitoes become infected by biting individuals who have these diesases, but after such infection they are ready to transmit it by their bites to individuals of the human race. Hence patients with malarial fever or with yellow fever must be screened against the possibility of mosquitoes becoming infected and thus transmitting the disease to others.

As just stated, terminal disinfection is now rarely necessary although fumigation may still be done in certain conditions. Fumigation of schoolrooms, however, and of school buildings, is an unnecessary expense. Spraying the floor and washing the region in which a child has been, when he developed an infectious disease, with antiseptics such as corrosive sublimate solutions and strong formaldehyde solutions, is the proper course to pursue. Books, pencils, etc. should generally be destroyed. If a book is valuable, it may be subjected to dry heat or placed in a formaldehyde cabinet.

With the object that the infecting agent must be confined to the patient's room and not be allowed to get out of it, and with the knowledge that the contagium is carried by some of the excretions or secretions of the body, the instructions of the physician to the nurse are for her to so dress that she cannot readily carry the germs; for her to properly cleanse her hands before eating or drinking; and for her to be sure that the patient's eat

ing utensils are placed in boiling water or otherwise thoroughly cleansed before they are allowed to be taken to other parts of the house. All secretions of the nose and throat and all sputum from coughing should be received on gauze or paper napkins, which should be immediately deposited in a paper bag, and the bag and contents be later burned. If the disease is one which is transmitted by coughing and spraying, when the nurse is near the patient she should wear a rather thick mask protection for the nose and mouth.

For the disinfection of the hands of the nurse, or others in attendance, a 1-1,000 solution of bichloride of mercury, or a 2.5 per cent. solution of phenol, or a 1.5 per cent. solution of chlorinated lime are efficient. When advisable, especially while the nurse is caring for the stools in cholera, dysentery, typhoid fever, and paratyphoid fever, it is well for her to wear rubber gloves, which she can cleanse and keep in sterile solutions.

The patient's urine should be passed into a receptacle containing a 5 per cent. chlorinated lime solution, or a 1-500 mercuric chloride solution. The urine should then be allowed to stand, covered, in this vessel for an hour or more before it is poured down the closet. The feces should be passed into the same solutions, but an equal quantity of a 25 per cent. chlorinated lime mixture should be added after the fecal matters have been broken up. The receptacle should then be covered and allowed to stand two hours or more before the contents are poured down the closet. The patient's buttocks may be cleansed with gauze wet with a 1-1,000 bichloride of mercury solution or a 2.5 per cent. phenol solution, unless the parts are irritated and sore. In this case, saturated solutions of boric acid may be used.

The strength of other solutions used to disinfect the excreta are: 5 per cent. phenol solutions; 3 per cent. cresol solutions; 5 per cent. copper sulphate solutions; and 5 per cent. solutions of the official Liquor Formaldehydi.

The clothing of the patient and the bed clothing should be placed in a 5 per cent. formaldehyde solution or in a 1-2,000 bichloride of mercury solution, and should remain in the

solution some hours before they are sent to the laundry, where they can be subsequently boiled.

With the understanding that the skin does not carry infection in the majority of contagious diseases, although it may be contaminated at some part by some secretion which carries infection being deposited upon it, general antiseptic baths are usually inadvisable until possibly just before the patient is to leave the contagious ward or the sick-room. At that time he may be bathed in a weak (1-10,000) solution of bichloride of mercury, if it seems advisable, afterwards bathed with boric acid solutions, and wrapped in an absolutely clean sheet before he goes into another room and puts on clean clothing. His hair should have been properly shampooed and cleansed before his bath. It should be remembered that the long tedious desquamation of scarlet fever does not carry the contagium of that disease.

The blankets, comfortables, and many equipments of the room, rugs, etc., may be steamed or dry heated to sterilization; or the whole room may be fumigated with formaldehyde or with sulphur. All doors, windows and other openings of the room must be sealed before fumigation. Five pounds of sulphur, best in so-called candles, for every thousand cubic feet of space are sufficient. When sulphur is burned, proper care should be taken to prevent fire; the burning sulphur should be placed in pans on islands surrounded by water, so that spitting of the burning sulphur cannot start a fire. There should also be steam from boiling water, or from a radiator, in the room for the best results of sulphur fumigation. Sulphur is the best disinfectant when lice, flies, or other insects may be the carrying source of the contagium. When there are no animal carriers of the particular disease, formaldehyde is the better fumigator.

One of the best methods for causing formaldehyde fumigation is to dissolve 75 grams of permanganate of potash in 90 mils of hot water; then 30 grams of paraformaldehyde is added. This causes continuous liberation of formaldehyde gas until the formaldehyde has been exhausted, and this amount is sufficient for disinfection of a thousand cubic feet. Dixon has suggested

substituting the following for the above, namely: pour together a pint of a saturated solution of formaldehyde gas and one and a half ounces of strong sulphuric acid. When this mixture has become cooled the solution is poured over 10 ounces of sodium dichromate crystals which is spread out in a thin layer in a large container.

No matter how thoroughly the fumigation is done, scrubbing and sunlight, if possible, should follow.

Formaldehyde.-Liquor Formaldehydi.—Solution of Formaldehyde (Formalin) is best procured in sealed bottles. The strength of the official preparation is 37 per cent. Formaldehyde solutions should never be used internally.

Action. The local action of a strong formaldehyde solution is irritant and painful, and if it is applied to the skin in full official strength, it must be quickly washed off or it will cause blistering. Even if weak solutions, as 2 or 3 per cent., are used repeatedly on the skin it will cause irritation, eczema, and perhaps dermatitis. It has been considered that 1 and 2 per cent. solutions were actively germicidal if the germs were subjected to the action of such solutions for an hour or more, but Hatcher and Wilbert state that it requires forty-five minutes for destruction of tubercle bacilli in a 5 per cent. solution. If the solution is hot, it acts more rapidly.

Toxic Action.-If formaldehyde gas is inhaled it is so irritant that it may cause swelling of the larynx, edema of the glottis, and suffocation. The gas, even in small amounts, will seriously irritate the nose, throat, and larynx, and cause reddening of the eyes. If a solution of formaldehyde (unless it is very weak) is taken into the stomach, it will act as an irritant poison and cause the usual symptoms of such a posion. If a very weak non-irritant solution is taken into the stomach it will retard digestion. If much of this substance is absorbed into the blood it may break up the hemoglobin and cause hemoglobinuria, and if very much is absorbed, nephritis may be caused.

Treatment of Poisoning.-When strong solutions are taken into the stomach the treatment is that of an irritant poison (see page 757). If there are signs of edema of the glottis from inhalation of the gas, intubation or tracheotomy must be done.