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liquid particles capable of transport by the circumambient
air/' but that "the breaking of minute gas bubbles on the
surface of a liquid consequent upon the generation of gas
within the body of the liquid is a potent cause" of such
suspension, and that therefore the stagnation of sewage or
constructive defects in sewers may form cesspools of putre-
faction in the sewers and generate gases which may form
these bubbles. Such defects in sewer construction are totally
unnecessary, and cesspool accumulations should, as I have
said, never be allowed.

In 1883 P- Miquel* published the results of his experi-
ments on the comparison between sewer and street air in

*"The Sidewalk Ventilators in New York City are almost an

*"Les Organismes Vivants de I'Atmosphere," Paris.


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Micro-Organisms in Sewer Air.

Paris, and from 1893 to 1899 he made periodical tests which
were given in the following table:


Country Air. City Street.
Year. Montsouris. H6tel de Ville. Sewer Air.

1893 285 8,435 5.01s

1894 230 9,775 2,920

1895 330 7.615 2,590

1896 6/205 3,965

1897 197 5410 3.875

1898 5,200 2,075

1899 6,595 2,910

Uffelmann experimented with a house drain in 1886-7,
taking nine samples at intervals during a year. He found
an average of 3 bacteria per liter of sewer air. Petri found
I bacterium and 3 molds in 100 liters of air in a Berlin sewer
on one occasion and no bacteria and i mold on another.

Carnelley and Haldane* made important studies on sewer
air in England in 1887. They found less bacteria in the
sewers than in the streets in almost all cases, averaging 9
per liter in the former and j6 in the latter. They conclud-
ed that "The micro-organisms in sewer air come entirely,
or nearly so, from the outside, and are not derived, or only
in relatively small numbers, from the sewer itself." They
found a considerable increase, however, under violent splash-
ing. Tfiey found less bacteria m the air in contact with
quietly flowing sewage rather than more, on account of the
wet surface.

Robertson** found less bacteria in the air of the sewers

•T. Carnelley and J. S. Haldane. "The Air of Sewers," proceed-
ing's of the Royai Society of London. 1887. XLiII. pp. 394 and 601.

•••'A Study of Micro-Orgranlsms in Air. E^speclally Those In
Sewer Air. ana a New Method of Demonstrating Them." British
lied. Journal. Dec. 15. 1888.

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of Penrith than in the street air, averaging 4 to 6 respec-
tively. More bacilli were found in the former and more
cocci in the latter.

Laws found that even splashing in sewers was unlikely
to produce appreciable infection, and that sewage falling
into an egg-shaped sewer, 11 ft. x 9, from the middle of
its height, produced practically no effect on the number
of germs.

J. McG. Smith (Sixth Annual Report of the Metropolitan
Board of Water Supply and Sewerage, 1893) found as an
average of 20 tests 225 germs per liter in the sewers of
Sydney, the particular forms being without exception organ-
isms common in street air.

In 1894 Dr. A. C. Abbott of Philadelphia found germs
were transported on a current having a velocity of 16.5 cm.
per minute, but not by one of 8.6 per minute or less. Dr.
Abbott's conclusions were that the danger of bacteria being
transmitted under natural conditions was practically negli-

Dr. Charles Harrington* says "The majority and the best
of German investigators, such as Fliigge, Rubner, Gartner,
Soyka, Prausnitz, and others maintain that sewer air and
sewer gases are quite incapable of conveying the germs of
typhoid fever and other infective diseases. It is true that
some of the gases given off in the putrefaction processes
which go on iii sewers are more or less poisonous, but
whether they are capable of producing any injurious defects
depends very much on the amount inhaled and on the degree
of concentration. In any event they are certainly incapable
of producing any infective disease in the absence of the
specific germ."

Mr. Allen Hazen writes that Col. Ruttan has "investigat-
ed the plumbing in a considerable series of houses in Win-

*A Manual of Practical Hygiene. Phils, and N. T.. 1901.


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nepeg with the general result of finding that plumbing is
not associated with typhoid fever. In fact his statistics
show a somewhat larger proportion of cases of typhoid fever
in the houses where the plumbing is good, than in those
places where it is defective."

Mr. Hazen sums up the best current American opinion
in the following sentence ** After many years of experience
and long continued investigation there is not the slightest
reason to believe that infectious diseases are carried by the
air of sewers."*

G. C Whipple** says "T)rphoid germs do not readily
leave a moist surface. Sticky by nature they adhere until
desiccation loosens their dead cells. For this reason sewer
air is not to be looked upon as a direct means of infection."

In 1907 Major W. H. Horrocks* of the Royal Army
Medical Corps of Great Britain in some analyses of sewer
air at Gibraltar found under certain conditions germs car-
ried from the sewage into the air. His principal deduction
from these tests was stated as follows: "Specific bacteria
present in sewage may be ejected into the air of ventilation
pipes, inspection chambers, drains and sewers by (a) the
bursting of bubbles at the surface of the sewage, (b) the
separation of dried particles from the walls of pipes, cham-
bers, and sewers, and probably by (c) the ejection of minute
droplets from flowing sewage."

This paper created some excitement among sanitarians in
the world, and caused many to return almost to the old time
terror of "sewer gas."

But closer examination of the experiments of Horrocks
and of his summary of conclusions does not appear to jus-

*En^neerinK News, LIII. 246.

••In the latest American Text Book on Typhoid Pever (Typhoid
F^ver. New York. 1908).

•Proceedings of the Royal Society. Series B. Vol. LXXIX, No. B
811. p. 2SS. Feb. 7. 1907.


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tify any such alarm. These conclusions as stated by himself '
were only such as had practically been admitted by previous
investigators we have already quoted.

In some of his experiments Major Hor rocks used strongly
foaming soapy solutions and vigorous splashing resulting
in the ejection of a few germs (B. prodigiosus) from the
sewage in the same way with other investigators. In an-
other case he obtained a few germs from quietly flowing
sewage. But this again had been observed by others and
ascribed to the drying of sewage on the sides of the pipes,
or from the transmission through it of fine bubbles caused
by decomposition or chemical action in the sewage. Certain
germs are known to dart rapidly through the fluids in which
they exist under the action of flagella, celia or whips at-
tached to their bodies. Others have a slow serpentine, spiral
or creeping motion and it might, at first thought, seem pos-
sible for the swiftly darting kinds to leap out of the water
Uke a flying fish and thus escape into the air. A flying fish
can leap from the water and remain a few moments in the
air. But the germ has' not the peculiar muscular, flexible,
and springy body, fins and tail of the flying fish. The long
flagella of the germ presents precisely the construction which
would prevent aerial flight especially when heavy with water
soaking. Cuttle and jelly fishes more nearly resemble the
flagellated bacteria and these do not fly about in the air. To
expect such action on the part of even the swiftest darting
germ would be as reasonable as to expect to see a devilfish
paddle himself with his long tentacles up to the surface of
the ocean and soar away above the clouds. Mariners have
not as yet recorded having seen this feat and microscopists
are as little likely to have to tell the tale about disease germs.
That germs do not progress by their own motive power
through air was indicated by Pasteur when he proved that
it was not necessary to insist upon hermetic sealing or cotton


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Micro-organisms in Sewer Air.

filters to keep them from gaining access to a flask of in-
fusion. It is now well known that if the neck of the flask
be drawn out into a long tube and turned downwards, and
then a little upwards, even though the end be left open, no
contamination will gain access. The force of gravity will
prevent them from ascending the long arm of the tube into
the neck of the flask and impregnating the infusion.

Moreover Major Horrock's bacterium prodigiosus has a
very slow and sluggish motion. His conclusion that germs
may probably escape from minute droplets ejected from
flowing sewag^e seems perfectly natural and requires no
special explanation.

A repetitipn of Major Horrock*s experiments by another
well known bacteriologist* recorded in the following table
showed similar results, and in this case also the germs eject-
ed were so few as to be, from a sanitary point of view, con-
sidering the great volume of the air into which they were
transmitted, entirely negligible, as he showed in various
ways and from th^ following table.


B. prodigiosus per liter.
Experiment. In liquid. In air.

I 630,000,000 0000

2 , 680,000,000 0000

3 230,000,000 0100

4 5,000,000,000 0130

5 1,000,000,000 0000

6 2,700,000,000 I o o I

7 1,800,000,000 000

8 4,400,000,000 000

He found that even under conditions of foaming and bub-
bling very favorable for ejecting bacteria into the air from

*See report of Prof. C. £2. A. Winslow's experiments for the
National Aasociatlon of Ifoster Plumbers.


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liquids containing many millions and even billions of bac-
teria per liter,'*^ the number so ejected was so very small as to
be practicaHy negligible. Most accurate methods of detection
were employed, so that there should be no question of detec-
tion of any germ released from the liquids swarming with
them. Prof. Newman** gives a provisional list of
normal sewage bacteria as follows: (i) Coli com-
munis, (2) proteus vulgaris, (3) B. enteriditis sporogencs,
(4) liquefying bacteria, B. subtilis and B. mesentericus, (5)
non-liquefying bacteria, (6) sarcinae, yeasts and moulds. No
pathogenic bacteria are included in this inventory. "Doubt-
less," he says, "such species (e. g., typhoid) not infrequently
find their way into sewage. But they are not normal hab-
itants, and though they struggle for survival, the keenness
of the competition among the dense crowds of saprophytes
makes existence almost impossible for them. * * ♦
There is no relationship between the microbes contained in
sewer air and those contained in sewage. Indeed, there is
a marked difference which forms a contrast as striking as
it is at first sight unexpected. The organisms isolated from
sewer air are those commonly present in the open air. Micro-
cocci and moulds predominate, whereas in sewage bacilli are
most numerous. * * * Pathogenic organisms and those
nearly allied to them are found in sewage, but absent in
sewer ain ** * * Lastly, only when there is splashing
in the sewage, or when bubbles are bursting (Frankland)
is it possible for sewage to part with its contained bacteria
to the air of sewers. * * * The interior of the cavity
of the mouth and external respiratory tracts is a moist
perimeter from the walls of which no organisms can rise
except under molecular disturbance. The position is pre-
cisely analogous to the germ-free sewer air as established

•About a quart

•* Demon Rtra tor of Bacteriology in King's College. I^ndon. In
his work entitled "Bacteria." published by John Murray. London,


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Micro-Organisms in Sewer Air.

by Messrs. Laws and Andrewes for the London City Coun-
cil. The popular idea that infection can be *given off by
the breath' is contrary to the laws of organismal pollution
of air. The required conditions are not fulfilled, and such
breath infection must be of extremely rare occurrence. The
air can only be infective when filled with organisms arising
from dried surfaces. The other series of investigations were
conducted by Drs. Hewlett and St. Clair Thomson, and
dealt with the fate of micro-organisms in inspired air and
micro-organisms in the healthy nose. They estimated that
from 1,500 to 14,000 bacteria were inspired every hour.
Yet, as we have pointed out, expired air contains practically
none at all. * * * From the two series of experiments
which we have now considered we may gather the follow-
ing facts :

(a) That air may contain great numbers of bacteria which

may be readily inspired.

(b) That in health those inspired do not pass beyond the

moist surface of the nasal and buccal cavities.

(c) That here there are various influences of a bactericidal

nature at work in defense of the individual.

(d) That expired air contains, as a rule, no bacteria what-


* * * "It should be noted that the bacilli of diphtheria
are capable of lengthened survival outside the body, and are
readily disseminated by very feeble air currents."

Miquel found during a six years' investigation of the air
of Paris an average of 4,000 bacteria per cubic meter in
that of Montsouris Park. Fliigge, taking an average of
the middle of the city, but only about a tenth as many in
100 bacteria per meter, estimates that "a man during a life-
time of seventy years inspires about ^5,000,000 bacteria, the
same number contained in a quarter of a liter of fresh milk."

The ntunber of bacteria in the air diminishes in cities rap-


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idly in proportion to the altitude, Miquel finding 750 per
cubic meter in the Rue de Rivoli, but only 28 at the summit
of the Pantheon. Whereas at the seashore there might
average a hundred per meter, the number diminishes as the
distance seaward increases, and the maximum distance sea-
ward, according to Dr. Fischer's experiments, to which
germs can be transported lies between 70 and 120 miles,
beyond which they are almost invariably absent. "Of par-
ticular interest in these experiments," says Frankland, "is
the very distinct manner in which they show that the micro-
organisms which are present in sea-water are not commu-
nicated to the air, excepting in the closest proximity to the
surface, even when the ocean is much disturbed."

All these facts co-operate to show that wet surfaces do
not give up their germs to the air under normal conditions.


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The Disconnecting Trap and the Reasons Why Its Use
Should Be Prohibited by Law.

HE fact that the air of sewers is
freer from all forms of micro-organisms
than is the outer air above them ac-
counts for the immunity with which peo-
ple may work in well ventilated sewers,
and explains the reason why the great
Paris sewers, for instance, are so safe,
visited every year by thousands of travel-
ers from all parts of the world, with no
case on record of resulting disease.
It has been related that the most re-
markably located hotel in the world was built in these Paris
sewers almost immediately beneatfi the Madeline church to
accommodate the municipal scavengers. The interior was
described as being singularly neat and clean, and as serving
between sixty and seventy breakfasts and dinners to the
workmen therein, and these sewer laborers are as healthy
as are any other class of laborers in the city.

In view of all the facts, it becomes evident that the dis-
connecting trap and its vent are really worse than unneces-
sary. They are a positive injury as obstructing ventilation
and waste discharge, as complicating the plumbing, as forc-
ing odors generated in poorly ventilated sewers directly into
the crowded streets, sometimes greatly to the annoyance of
the people, and, above all, of depriving us of one of the
most effective means now known of filtering the air of
aties and towns of dust and disease germs. Their use


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should therefore be prohibited by law so that every soil
pipe may serve as an effective means of ventilating the
sewers and reducing the number of floating impurities in
the outer air. This latter advantage- 1 have not as yet seen
advanced, though it is of the utmost importance, especially
in times of epidemics.

So important is this matter and yet so little is it under-
stood by, the public that we ought to call a little further at-
tention to some of the more recent investigations which
have been made into the number and kind of bacteria found
in the air of the streets and as to their fate when they find
access into the sewers through the ventilating inlets.

Analyses of the air in the Paris sewers have been regu-
larly made at stated intervals and it is found that this air
contains on the average more carbonic acid and ammoniacal
nitrogen than the street air, but only half as many germs
of any kind, while most of the investigators have failed to
find any disease germs at all there. In these investigations
it has been found also that the humidity in the sewers is
great and practically constant.

In the air of the sewers of Berlin Petri found that there
were only a very small number of micro-organisms as com-
pared with that of the streets.

Similar results were obtained by other investigators in
the sewers of London, Dundee, Westminster, Bristol and
Sydney in Great Britain, where classifications of the various
kinds of bacteria were made. In all these researches it was
found that sewer air is, as far as germs are concerned, very
much purer than outside air, and that these germs came not
from the sewer but from the outer air; that a decrease in
the number of germs in the outer air was followed by their
decrease in the sewer air; that the kind of germs in the
sewer air was the same as that in the outer air, but differ-
ent from those contained in the sewage itself. Laws and
Andrewes, who were commissioned by the county council


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Disconnecting Trap Should be Prohibited by Law,

to study the bacteria in the London sewers, state that the
number of micro-organisms existing in sewer air appears
to be entirely dependent upon the number existing in the
outer air at the same time and in the same vicinity. They
say that if the organisms existing in sewer air were derived
from those existing in sewage, then the flora of sewer air
should bear a very close resemblance to the flora of the
sewage, but that they in reality bear no resemblance what-
ever to one another. They say, indeed, "we may go even
further and state that, as far as we are aware, not a single
colony of any of those species which we have found pre-
dominant in sewage has been isolated from sewer air. We
consider, therefore, that the study of the sewage bacteria
on which we have been engaged fully confirms the conclu-
sions previously arrived at from the study of the micro-
organisms of sewer air, viz., that there is no relationship
between the organisms of sewer air and sewage." * * ♦
"In the conclusions to Part I of this report we endeav-
ored to show that sewer air has no power of taking up
bacteria from the sewage with which it is in contact . A
strong argument in favor of this view is the fact that the
very organisms which are most abundant in sewage are
precisely those which are absent from sewer air. In the
course of previous experiments on sewer air, the nature of
the organisms in some 1,200 liters of sewer air was care-
fully determined. Not once was the bacillus coli communis
or any of the predominant organisms of sewage found,
though we have shown above that the former is present in
sewage in numbers varying from 20,000 to 200,000 per cubic
centimeter. If this be so, how infinitely improbable becomes
the existence of the typhoid bacillus in the air of our sewers.
That sewage* is a common medium for the dissemination

•This is before the disease g'erms are destroyed in the sewers
by coming In contact wtih the other bacteria which find in sewage
their natural element ao4 which are non-pathogenic


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Plumbing and Household Sanitation.

of typhoid is certain; that sewage-polluted soil may give
up germs to subsoil air is possible ; but that the air of sewers
themselves should play any part in the conveyance of ty-
phoid fever appears to us, as the results of our investiga-
tions, in the highest degree unlikely."

Now the house drains and soil pipes, being much smaller
and longer in proportion to their sectional area, and being
more uniformly moistened on their inner surfaces when in
use, and having more bends and angles in proportion to
their length than the public sewers, are correspondingly
more effective in removing any bacteria which may enter
them from the sewers. Hence the air of the house drains
will, as is quite evident, and as I shall endeavor to make
visible by experiments, be found to be still freer from
germs than even that of the sewers themselves.

As has already been pointed out, the danger from the
inspiration of sewer air is generally believed to lie in pre-
disposing the system to harm from disease germs coming
from other sources. This predisposition is probably due
to the gases given out by putrid fermentation, such as
carbonic acid, ammonia, sulphurated hydrogen, hydro car-
bons and volatile fatty acids, and the danger is in propor-
tion to the concentration of these poisonous matters. This
danger may be reduced to a minimum or altogether re-
moved by thorough ventilation. In order to provide a sim-
ple ocular demonstration of the manner in which sewage
and the moist surfaces of sewers arrest these fine particles
when they are brought in contact with them, gradually
clearing the air of them entirely, I constructed several ex-
perimental drain pipes of metal and glass tubing and of
different lengths, varying from ten to twenty-five feet, some
being straight and others bent.

These pipes were thoroughly moistened on the inside


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Disconnecting Trap Should be Prohibited by Law,

with water, and a specified quantity of dry fine dust was
placed at one end of each^ and the attempt was made to
blow the dust through the pipes from end to end by means
of bellows. Before describing our experiments it is im-
portant to point out the relation which dust bears to disease
and how it serves to disseminate bacteria through the air.
Mrs, Frankland* says in her most valuable work, entitled
"Bacteria in Daily Life," published in 1903: "That it is
no exaggeration to describe streets from the bacterial point
of view as slums is to be gathered from the fact that much
less than a thimbleful of that dust which is associated with
the blustering days of March and the scorching pavements
of summer may contain from nine hundred to one hundred
and sixty millions of bacteria. But investigators have not
been content to merely quantitatively examine street dust;
in addition to estimating the numerical strength of these
dust battalions, the individual characteristics of their units
have been exhaustively studied, and the capacity for work,
beneficent or otherwise, possessed by them has been care-
fully recorded. The qualitative discrimination of the bac-
teria present in dust has resulted in the discovery of, among
other disease germs, the consumption bacillus, the lockjaw
or tetanus bacilli, bacteria associated with diphtheria, ty-
phoid fever, pulmonary affections and various septic proc-
ess. Such is the appetizing menu which dust furnishes for
our delectation. There can be no doubt, therefore, that
dust forms a very important distributing agent for micro-
organisms, dust particles, aided by the wind, being to bac-
teria what the modern motor-car, with its benzine or elec-
tric current, is to the ambitious itinerant of the present
day. Attached to dust, bacteria get transmitted with the

•Mrs. Percy Frankland. Fellow of the Royal Microscopical Soci-
ety, Honorarv Member of Bedford College, UnWersity of London.
and Joint author with Professor Frankland of "Micro-Organisms in
Water/' **The Life of Pasteur/' eta


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Plumbing and Household Sanitation.

greatest facility from place to place, and hence the signifi-

Online LibraryJohn Pickering PutnamPlumbing and household sanitation → online text (page 8 of 40)