_DISINFECTION_
Inasmuch as more than 10 per cent of all deaths are due to bacterial or
to various infectious diseases, it is of considerable interest to study
the various means by which these germ diseases may be prevented. In this
chapter it is proposed to discuss the different ways in which the active
agents concerned in the spread of disease may be captured and put to
death. It has already been pointed out that infectious diseases can be
acquired only by the introduction of the specific germs into the human
body, either through the mouth or lungs or through some skin abrasion.
Further than this, it is quite as definitely known that the vitality of
the germ after leaving a diseased person depends primarily upon its
condition at the time of leaving the body and afterwards upon the
environment which that germ finds outside of the affected person, while
waiting for a chance to make its next human resting place.
It is evident, therefore, that if during the interval which elapses
between the time when the germs leave a sick person and the time when
they enter another person some method could be found by which these
germs could be killed, the progress of the disease would be effectually
stopped.
This, in the most general sense, is what is meant by disinfection. It
is a determined effort to destroy the carriers of disease while
temporarily absent from the human body which is their natural home. This
process of killing bacteria, however, is not so simple a matter as it
might at first seem. They are, unfortunately, such minute beings that
they cannot be seen, so that the warfare is waged against an invisible
enemy, not, however, to be despised on that account. The methods of
warfare must be uncertain, since the exact location of the enemy cannot
be known, and it is manifestly impossible to disinfect the universe.
What is done is to fix upon the location or surroundings where the
original patient was confined, and, assuming that the germs, if any,
which have escaped ready for further infection are somewhere near, to
poison the air and the wall and floor of the room in question so that
happily the germs may be killed.
_Disinfecting agents._
The various agents used to destroy those germs which are carriers of
disease may be divided into two groups, namely, heat in its various
forms, and chemicals. Literally, the word "disinfection" means "doing
away with infection," so that to disinfect a room is to do away with the
infection present in the room. It has, however, come to have a more
general meaning than this and is commonly used instead of the word
"destroy," so that a disinfecting solution is the same thing as a
destroying solution, applied, of course, to bacteria.
It has already been explained that by far the majority of bacteria are
useful if not essential to human life, and one of the difficulties in
employing disinfecting or destroying solutions is that they put an end
at the same time to both useless and useful bacteria. As an example,
the fermentation processes in the human intestines are accompanied if
not produced by certain kinds of bacteria, although on occasion these
harmless or useful bacteria may develop into most obnoxious germs,
producing unpleasant fermentation. It might be easy enough for a doctor
to make a patient swallow some antiseptic solution, like carbolic acid
or corrosive sublimate or nitrate of silver, for the purpose of getting
rid of certain undesirable bacteria in the intestines, but it does not
need a doctor to know that for a patient to swallow such active poisons
as these would not merely kill the harmful bacteria and the good ones as
well, but probably the patient himself.
_Antiseptics._
There is another word often used in connection with bacteria, namely,
"antiseptic," and the common significance of this word applies to a
substance which interferes with or retards the growth of bacteria
without actually destroying them. Doctors, for instance, use antiseptic
instead of disinfecting solutions on wounds, not because they do not
wish to kill the pus-forming bacteria, but because the antiseptic
solution will prevent their growth and not be, as a disinfecting
solution, harmful to the cells which he is trying to repair. It would be
folly, for example, to inject a strong 50 per cent solution of carbolic
acid into a wound on the arm produced by a saw, because all the energy
of the vital forces at the seat of the wound are needed for repairs, and
there is none to spare for so active a detergent as carbolic acid. An
antiseptic, on the other hand, is mild enough so that it does not act on
the tissue at all, but merely prevents any undesirable growth of
bacteria.
_Deodorizers._
There are substances used, perhaps not so much around country houses as
around city houses and in water-closets, which are neither disinfectants
nor antiseptic, but act as deodorizers only. Such a substance, for
example, may be thrown into the kitchen sink, not at all for the purpose
of killing bacteria, but for disguising the smell from the cesspool into
which the sink-wastes discharge. It has no disinfecting properties and
is good for nothing unless the material is so scented as to be agreeable
on that score. One of the frauds perpetrated on the public is the
preparation and sale of the various appliances designed and regulated to
produce a perpetual smell and claimed on that account to be either
disinfecting or antiseptic agents. The smell is worth nothing.
_Patented disinfectants._
The poison of the disinfectant or antiseptic, whether it be in liquid or
in gas form, is the essence of the material, and since the value of
disinfectants is based on the crude raw materials which any one can buy,
it is clearly unnecessary to buy expensive patented solutions for
disinfectants when ordinary lime or carbolic acid are equally as good
and can be had at much lower prices.
A disinfecting solution, to be successful in its action, must be
reasonably proportioned in volume to the amount of material to be
disinfected, whether this be a liquid or clothing or the air of a room.
It is the height of absurdity, for instance, to pretend to disinfect the
air of a large room by burning a tablespoonful of sulfur on a shovel in
the center of a room without even taking the trouble to close the door.
It is absurd to attempt to disinfect the bed linen in a single pailful
of hot water, since even if the water was hot at the beginning, it would
be so reduced in temperature by the first piece that went in that its
efficacy would be lost for everything else. It is equally absurd that a
liquid from a bottle, no matter how much advertised, can effectually
disinfect a room, either by a gentle sprinkling of the liquid on the
walls and floor or by a more thorough spraying of the air with an
atomizer containing the liquid.
_Disinfecting gases._
Two gases are available for use in disinfection, and these are valuable
particularly in killing germs left in a room after a patient suffering
from an infectious disease has been removed. The diseases referred to in
the following chapters are all of this nature, and one of these two
gases ought to be used in every case; otherwise the room may continue to
harbor germs of the disease for months or years with the possibility of
infecting a future tenant at a time when his vitality was such as to
make him an easy prey. Nor must the contents of the room be overlooked.
The writer was recently told of a large family where one child had
scarlet fever, recovering in September. The sick room was thoroughly
disinfected, but the careful housewife, fearing damage to her blankets,
had taken them to the attic before disinfection began. In the cold
weather of February these blankets were brought down, and in six days
the two children sleeping under them had contracted the disease.
_Sulfur as a disinfectant._
When sulfur is burned, a gas is formed known as sulfurous acid, and
until the last few years, it was the most common of all disinfecting
agencies. The writer well remembers that when about to visit a city in
South America infested with yellow fever, he was seriously advised to
fill the inside of his shoes with sulfur as a precaution against the
disease. He might as well have worn a red ribbon on his hat so far as
any protection went, but it illustrates the confidence formerly shown in
sulfur as a disinfectant.
It is now known that in the dry, powdered state, sulfur is of no value
unless, perhaps, the germs be smothered with the sulfur flour. When
burned, however, the gas given off has a certain disinfecting property,
although this is limited. It has almost no power of penetrating into
curtains, blankets, and upholstered furniture, although the penetration
is decidedly increased if these objects are moistened either by steam or
by water vapor. The proper amount of sulfur to be burned for any room is
at the rate of 3 pounds per 1000 cubic feet of air space in the room.
Thus, if a room be 12 feet by 15 feet and 8 feet high, containing 1440
cubic feet, it would be necessary to burn 144/100 of 3 pounds, or 4-1/3
pounds.
Before undertaking to disinfect a room with sulfur, it should be made
thoroughly air-tight, and this must be done carefully, not merely by
closing the larger and obvious openings, like doors and windows, but by
pasting strips of paper over every crack which might allow air to
escape. Thus the four edges of the window sash must be pasted up, and a
strip must close the crack between the two sashes. All the doors but the
one reserved for exit should be pasted up from the inside, and finally
this last door pasted up on the outside. If the floor has settled away
from the base-board, the cracks thus made must be pasted up. In short,
the room must be made absolutely air-tight. The room should be left thus
closed for at least twenty-four hours, and since there is some danger
from fire, a proper provision should be made for the burning sulfur.
This can be done by placing an old milk pan (a most convenient object in
which to burn the sulfur) on a couple of bricks, which may be set inside
a wash tub with perhaps three or four inches of water in the tub. The
most convenient way of ignition is to moisten the sulfur with a little
alcohol which can be readily set on fire.
Since clothes of every sort are more effectually acted upon when moist,
they should be sprinkled with a hand atomizer just as the sulfur is
lighted, and this should always be done in the case of any stuffed
furniture or hangings. Anything that can be removed should be taken out
and sterilized by steam, since live steam is the only disinfecting agent
which will penetrate such things as mattresses, pillows, and rolled-up
bundles of every sort, and with these last even steam is not certain. It
is far safer to send a mattress to the cleaner to be steamed than to try
to sterilize such bulky objects at home. It requires about twenty-four
hours with the room tightly closed to generate enough gas so that the
bacteria which may have found their way onto the walls or floor or
ceiling or into the air of a room will be surely killed. After that time
the room can be opened and then the usual household cleansing processes
carried out as an additional safeguard. It is a wise measure in the case
of infectious diseases, even after a room has been fumigated with
sulfurous gas, to wipe off the woodwork and the walls, if their
construction allows it, with a solution of carbolic acid, since in this
way the germs which have accumulated on the woodwork will certainly be
killed.
_Formaldehyde disinfectant._
Formaldehyde is the other gas which is commonly used for disinfecting
the air of a room. It is most readily produced by buying solidified
formaldehyde and then decomposing it by the action of heat. Formaldehyde
candles, as they are called, may be purchased at almost any drug store,
and while special forms of generating stoves may be found in the open
market, an ordinary heating apparatus of almost any sort will answer the
purpose of decomposing the solid formaldehyde. About 20 ounces of the
formalin should be used for each 1000 cubic feet of space. With this
agent, however, as with sulfur, the penetrating power of the gas is not
very great, and such things as mattresses and clothing should be sent to
a steam sterilizer rather than be trusted solely to the power of the
formaldehyde.
In using this gas, the same care about pasting up cracks and crevices in
the room should be followed as already prescribed for the use of sulfur,
and, as with sulfur, a reasonable precaution against fire should be
taken by placing the apparatus in a tub of water or in a large pan of
sand where accidents cannot happen. The room should be kept closed for
at least twelve hours, and then should be thoroughly aired, and if the
room is to be used again soon, the disagreeable odor may be removed by
the free use of ammonia, either sprinkling it around in the room or by
placing about saucers of ammonia.
_Liquid disinfectants._
More common than gases and most readily suggested as disinfectants are
certain liquids which have been proved both by laboratory
experimentation and by actual experience to have the power of killing
bacteria when brought into contact with them. Those liquids which have
commended themselves particularly have additional advantages in not
destroying fabrics, metals, or tissue with which they are brought in
contact and in being purchasable at moderate prices.
There is little choice between a number of such liquids, and the number
of modifications or combinations which are made and bottled and sold
under some fancy name is legion. But the label, the name, and the
additional price add nothing to the value of the basic chemical from
which they are all compounded, and except for their convenience, they
have little to recommend them.
_Carbolic acid as disinfectant._
Carbolic acid is one of the most useful of these liquids, and in its
various forms appears in almost all disinfectants. It may be obtained
from the drug store in two forms, either as a crystal or as a
concentrated solution.
A 2 per cent solution, that is, one pint of carbolic acid to six gallons
of water, is the proper strength for all such uses as wiping off wooden
surfaces, furniture, floors, etc. A stronger (5 per cent) solution is
used when it is intended to destroy organic matter containing large
quantities of germs. This is practically a saturated solution, so that
if a bottle be partly filled with the crystals of carbolic acid and then
completely filled with water, the water will absorb enough of the
carbolic acid to make a 5 per cent solution, and the water may be poured
on and off as long as the crystals remain. This 5 per cent solution is
the proper strength to receive sputum from tuberculous patients,
material ejected from the stomach in diphtheria, and fecal matter from
typhoid and cholera patients. This strong solution should not be used
on the living human body, since it is powerful enough to eat directly
into the flesh, and being a violent poison, it should be kept out of the
way of the household and carefully labeled to avoid accidents.
Carbolic acid has no value at all in the way of disinfecting the air,
although fifty years ago surgeons were accustomed to use a spray of
carbolic acid around the operating table before an operation in order to
destroy any germs of the air lingering in the vicinity. It is equally
futile to pour carbolic acid into sewers or to stand it around on the
mantelpiece for the purpose of disinfecting a room. Nor are sheets wet
in carbolic acid and hung over doorways and at the end of passages
anything more than a remnant of medievalism.
_Coal-tar products._
There are certain preparations made from coal-tar which, either alone or
combined with carbolic acid, have very strong disinfecting properties
and which are the bases of most of the patented disinfecting solutions
now sold. They are commonly called cresols or creosols and a 4 per cent
solution of any of the three ordinary forms will destroy bacteria in a
few hours. They are commonly used for receiving organic excretions of
sick persons in the same way as carbolic acid is used, and have about
three times the power of carbolic acid to destroy bacteria.
They have one great advantage besides the strength mentioned, in that
they are not materially affected or interfered with by the presence of
albuminous material. Carbolic acid in the presence of albuminous
material, like sputum, for instance, has the strength of the
disinfectant partly used up in combining with this albuminous material
so that the strength remaining for disinfection is weakened, and the
result is not as satisfactory as it would otherwise be. The coal-tar
products, on the other hand, are not so interfered with, and the
solution acts in full strength upon the bacteria.
_Mercury for disinfectant._
Corrosive sublimate, or bichloride of mercury, is one of the most active
poisons known and is as effective in dealing with the microscopic
organisms known as bacteria as it is in dealing with the larger animals
for which it has been used for years past,--the destruction of bed-bugs.
For general cleaning purposes, such as scrubbing woodwork, floors, and
walls, it should be used in strength of about 1 part to 3000 parts of
water. This means that for 1 ounce of corrosive sublimate 3000 ounces of
water or 25 gallons must be taken. This solution is very active in its
effect on all metal, so that it must be kept in brassware or
earthenware, and when mixed with the material which it is intended to
disinfect, it must be kept from tin or iron. This solution is also
affected by albuminous material, although this may be counteracted by
the addition of salt. It is a good plan, therefore, to add to the
solution salt at the rate of about 4 teaspoonfuls to each gallon of
solution. On account of the very poisonous action of this solution great
care must be taken to keep it away from children, and it has been
suggested that it is desirable to add some coloring matter to the
liquid, since without this it may be mistaken for clear water.
_Lime for disinfecting._
Chloride of lime is one of the most useful as well as one of the
cheapest disinfectants available. It costs about $25 a ton, although by
the pound this wholesale price would not be obtained. It is effective in
a 1 per cent solution, that is, 1 pound of chloride of lime to 100
pounds or 12 gallons of water. To be effective, the solution must be
well stirred into the organic matter to be disinfected, since it is the
chloride rather than the lime which is the disinfecting agent. Saucers
or soup plates of chloride of lime standing around the room have no
effect upon the germs in the air and on the floor and are of no more
value than sulfur, or roses for that matter. Chloride of lime is
commonly known as bleaching powder, and its effects on clothes or on any
substance which can be eroded is well known. It is, therefore, not a
suitable material for disinfecting towels, because the action is on the
towel as well as on the bacteria, differing in this respect from
mercury, which does not hurt the fiber of clothes.
Milk of lime is produced by slaking ordinary building lime until a fine
white powder is obtained, about an equal quantity of water to the amount
of lime to be slaked being necessary. When the powder has formed and
steam has ceased to be given off, then about four gallons of water
should be added to each gallon of the powder and the mixture well
stirred. This will probably always leave some lime in the bottom of the
vessel, since limewater is a saturated solution, and these proportions
furnish more lime than is necessary. If not too thin, it is a good
whitewash and is a most important agent when used as a whitewash in
disinfecting walls and ceilings of such rooms as hospitals and cellars
and other places where have been contagious diseases. Milk of lime is an
admirable disinfectant in the sick room and generally in houses where
infectious diseases have been. It may be poured down drains, into
water-closets and privies, and used liberally in all places where
bacteria may be supposed to thrive. It must come into intimate contact,
however, with the bacteria, and merely sprinkling a little lime dry
around the borders of a gutter or drain is of no value. The writer saw,
not long ago, a chicken yard where the inspector of a health department
had undertaken to secure disinfection by a generous sprinkling of white
lime powder around the yard. Such a procedure, however, is not
effective, but in a drain the dry powder might be of value because it
would later become effective when washed in solution into the drain.
Ordinarily, the dry powder is to be avoided.
_Soap as an antiseptic._
No better antiseptic exists than ordinary soap, not altogether because
of the properties of the soap, but because of the action of the soap
combined with hot water. Washing soda, dissolved in water and used for
boiling clothes which have become polluted, adds to the disinfecting
power of the hot water the disinfecting properties of the soap, and the
result is most effective. Ammonia has not the same value as the soda or
potash soap, although it has the power of destroying bacteria in the
course of a few hours.
It may not be out of place to emphasize the value of soap, not
particularly in times of epidemic or contagious disease, but as a
continual safeguard against infection. A large proportion of the
contagious diseases are probably the result of infected fingers or hands
coming in contact with the mouth and leaving there the germs of
infection. One of the first things a surgeon learns, in order to avoid
any possible infection of wounds or of openings which he makes for an
operation, is to thoroughly wash his hands in order to remove therefrom
all possible germs. He scrubs his hands, particularly his finger nails,
with soap and water and then bathes them in a solution of bichloride of
mercury before touching the patient in any place where infection might
occur. The difficulty, even with this great care, of freeing their hands
from bacteria has been found to be so great that, in late years,
surgeons have preferred to use, during operations, thin rubber gloves
which can be boiled before using and can be soaked in a stronger
antiseptic than the hands could bear.
It is extraordinary, from the standpoint of self-infection, to see how
men can be so careless as to sit down to dinner, after having worked in
places where their hands have come in contact with all sorts of organic
filth, without stopping to wash those hands even in cold water. It is
certainly providential that disease germs are as uncommon as they are,
for with the careless habits of most people in putting their hands to
their mouths, the death-rate from infectious diseases would be much
higher than it is except for the fact that most of the germs thus
introduced into the mouth are not disease-producing.
_Disinfecting by heat._
Better than any chemical agent known to be a destroyer of bacteria is
heat in one form or another. This may be steam or hot water or dry heat.
If a high enough temperature is maintained for a sufficient length of
time, the action is absolutely destructive to all germs. Fire does, of
course, destroy bacteria along with whatever material the bacteria are
concealed in, but such a disinfectant is of little value for ordinary
purposes, since the object of disinfection is to destroy bacteria
without destroying the surface on which they are lodged. In some old
buildings, where consumption or smallpox, for example, has become
permanent, it may be that the surest way of killing all the bacteria is
to burn up the house.
_Dry heat._
Unfortunately, even a moderate heat cannot always be applied. One's
hands, for example, can neither be heated in an oven to the necessary
temperature for destroying bacteria in their pores, nor can they be
immersed in boiling water or steam for a sufficient time to secure
thorough disinfection. Therefore, with the body, chemical means for
disinfection must be employed. Also when it is desired to disinfect a
liquid, such as beef broth, in which the experimenter desires to grow
some particular species to the exclusion of all others, dry heat is
inapplicable because it would evaporate the liquid, nor is chemical
disinfection possible because of its antiseptic effect on the bacteria
to be cultivated. Moist heat, therefore, must be used. When dry heat is
used, it is usually for the disinfection of glassware or earthenware or
metallic objects, the quality of which will not be affected by the
necessary temperature, namely, 150 degrees Centigrade, or about 300
degrees Fahrenheit. This temperature must be maintained for at least an
hour, and it is not certain even then to penetrate in full power to the
middle of blankets or comfortables. Except for glassware to be used in a
laboratory, dry heat, such as would be obtained by a kitchen oven, is
not to be recommended.
_Boiling water._
Boiling water, on the other hand, is the most effective and penetrating
disinfecting agent available. One has only to expose an object to
boiling water for five minutes to absolutely kill all disease-bearing
bacteria contained, and since bed linen, clothes, blankets, and such
articles as are naturally used in a sick room have to be washed after a
patient's recovery, it requires but very little additional trouble to
subject the soiled articles to that temperature of the water which will
secure disinfection at the same time. But the water must be boiling. The
mere fact that it was once boiling water gives it, half an hour later,
no disinfecting properties, and complete disinfection can be secured
only by actually boiling the garments or articles for at least five
minutes. The apparatus necessary therefore--and no better piece of
disinfecting apparatus can be secured anywhere--is a good old-fashioned
wash boiler. The action is more certain, that is, more penetrating, if a
little washing soda is added to the water at the rate of a tablespoonful
of soda to a gallon of water. This solution is admirable for washing
dishes, spoons, knives, forks, and other eating utensils used by sick
persons. It is always a mistake to wash dishes from the sick room in the
same vessel with other dishes. They should not only be washed
separately, but they should be washed in boiling water, and preferably
in a soap solution as just described.
_Steam._
For some purposes, steam is better even than hot water; its effect on
cotton and woolen garments is not so disastrous. A comfortable or
blanket, for instance, may be subjected to steam without losing its
elastic quality, and for small garments, an ordinary steamer, such as
is used for puddings, answers admirably. Cities use steam sterilizers
because of the greater convenience in furnishing steam to a large tank
as compared with filling and emptying a tank with water and then
providing sufficient heat to boil that water. The exposure to steam
should last from half an hour to an hour, depending on whether the
objects to be disinfected are small, open, and loose, or large, compact,
and dense. Some articles, like bales of rugs, rolls of wool, and large
bundles of cloth, cannot be sterilized at the center by ordinary steam,
and while it is not likely that infection at the centers of such tightly
rolled bundles has occurred if exposure took place while rolled up, yet
it is certain that the disinfection does not reach these centers. In the
case of such bundles as rugs from infected countries, where any single
rug may become the medium of infection, it is requisite to thoroughly
sterilize all parts of the bundle. For this purpose, it is necessary not
merely to expose the articles to live steam, but to have the live steam
under pressure so that it is forced into the inside of the packages by
an excess of external pressure. This is probably not available in an
ordinary house, where boiling must continue to be the method of
disinfection.
_Drying, light, and soil._
Before leaving this chapter, three agencies for disinfection may be
pointed out, not perhaps to be depended on, but in order that the kindly
provisions of nature may be appreciated. All germs removed from the
body, which is their natural home, and exposed to the air are subject to
drying and thus are killed. Unfortunately, this does not become true
except after long periods of time, nor is it equally true with all
germs, but it is certainly one of the methods by which the evil effects
of disease germs may be lessened. The germ of consumption lasts as long
as any germ, and yet this, when dried in the street, loses its vitality
after about a week. Similarly, the typhoid fever germs, unless kept in a
moist condition, dry up and die in a few days. With the drying, however,
comes the danger that in the process they may be lifted by the wind and
carried in the air to the mouths or nostrils of well persons, so that it
is not wise to depend solely on this method of disinfection.
Sunlight is more positive than the wind, and the exposure to direct
sunlight of a bottle filled with disease germs will kill them all in two
or three hours. The surface layers of a pond never have as many bacteria
in them as the lower layers, partly on account of the sedimentation, but
largely because they are killed by the direct action of sunlight. The
bacillus of consumption and bacillus of diphtheria are both killed in an
hour or so by direct sunlight. This is one reason why living rooms
should have sunny exposure and why, on the other hand, disease thrives
in dark tenements.
The soil is the third natural method of disinfection, not because the
soil itself destroys bacteria, but because in the soil are to be found
millions of non-harmful germs and these germs are hostile to the
disease-producing germs, so that they destroy their virulence. It is on
this principle that the wastes from typhoid fever patients are buried in
the garden, the presumption being that the bacteria there present will
destroy the typhoid fever germs before they can escape and do any harm.
While this action undoubtedly exists, it is not positive enough to
depend upon, and disinfection by the use of chemicals should always be
practiced.