Reprint from the ST. LOUIS CLINIQUE of June, 1891. 
Air and Contact Infection. 
Ji/ 
Translated from Schimmelbnsch’s ‘‘Aseptische Wundbeandlnng, ’ ’ with permission of the Author. 
BY FRANK J. M. D., 
Demonstrator of Bacteriology. Medical and Dental Depanment University of Buffalo. 
More ancient still than medical science 
itself, is the belief in the transmission 
of disease through the air. In surgery 
the opinion was long prevalent that 
wound infection was dependent upon an 
atmospheric influence, and this view be- 
came a dogma after John Hunter attri- 
buted the invariable absence of fever 
and suppuration in subcutaneous inju- 
ries, such as simple fractures, to the 
fact of their not having been encoun- 
tered by the air. When, in former 
times, cases in a hospital developed 
fever and suppuration, it was the con- 
taminated air of the ward which the 
surgeon regarded as the source of all 
evil. The whole aim of surgery in the 
recommendations of the so-called subcu- 
taneous method of operating, introduc- 
ing the instruments through the smallest 
possible slit-like opening, to divide, in 
a groping way tissues, tendons, and 
saw through bone, is in accordance with 
the endeavor to imitate the character of 
subcutaneous injuries, and procure 
wounds to which the air has no entrance. 
Against nothing else than the air it- 
self did Lister direct his first endeavors 
at asepsis—not against the air as a gas, 
however, but rather against the ele- 
ments of infection contained in the air 
which, he supposed, induced in like 
manner decomposition in the wound’s 
secretions and in the wound itself, as 
they produced changes and decompos- 
ition everywhere in organic material. 
Thus began Lister in his first commu- 
nication in the Lancet, 1867, regarding 
a new method of treating compound 
fractures and abscesses: 
‘‘The almost invariable absence of 
danger in simple fractures stands in 
striking contrast to the disastrous re- 
sults we otherwise often have occasion 
to observe, and the excessive frequency 
of which is one of the most grave and 
appalling incidents of surgical practice. 
Investigating the prime reason why the 
wound in a compound fracture may 
prove so disastrous, we find simply as 
explanatory, the septic changes of the 
blood which is poured out in greater or 2 
FRANK J. THORNBU ff 
less quantity around the seat of fracture 
and into the connective tissue spaces, 
such changes being induced by the 
entrance of air, the blood losing its mild 
character to take on the quality of an 
active irritant and become capable of 
producing local and constitutional dis- 
turbances.” As had been taught by the 
investigation of Pasteur, Schwann, von 
Dusch and others, organic material, 
blood and tissues, may be preserved 
from decomposition by protecting them 
from contact of the minutest living or- 
ganisms ; so also did Lister in his new 
method, endeavor to exclude from the 
wound the germs of decomposition. 
He irrigated the latter with carbolic 
acid with the use of which in counter- 
acting decomposition he had-had an 
astonishing experience in the dl§>rdor- 
ization of the fields over which the con- 
tents of sewers wrere allowed to slowly 
flow and settle outside the city of Car- 
lisle—in order to destroy the germs 
which the air had already carried into 
the wound. He then applied the dress- 
ings which were already saturated with 
carbolic acid, and with the greatest 
possible care bandaged-in the entire 
wound, occluding it completely with a 
layer of impermeable material so that 
further entrance of germs from the air 
would be prevented. During the oper- 
ation and at the subsequent change of 
dressing, the carbolized spray, in addi- 
tion, was disseminated over the entire 
region of the wound, this being intended 
to place the w7ound in an atmosphere 
which would be entirely free from dan- 
gerous organisms of every variety. 
At the time when Lister made the 
first practical trial of his new method 
of treatment, our knowledge of the 
germs contained in the air was very 
limited. That they existed as the min- 
utest forms of matter had, it is true, 
been recognized, but regarding their 
extent, morphological characteristics 
and appearance and their requirements 
for existence, almost nothing was known. 
It is true Tyndall has shown that they 
appertain to the sunbeams which be- 
come visible when the rays of light fall 
into a dark room through a crack in the 
closed window shutter; it is also a fact 
that Pasteur aspirated air through 
gun cotton and filtered out the germs, 
then dissolved the gun cotton in ether 
and examined it microscopically, and 
that Pouchet collected the particles of 
air-dust on moist plates against which 
the air was blown, but all these inves- 
tigations have proven of but little avail. 
From the fact that, in a comparatively 
short time, we have attained a quite 
thorough and more or less complete 
understanding of the extent, size, form, 
appearance and manner of life of the 
air bacteria, wre are indebted to nothing 
other than the brilliantly perfected 
methods of bacteriological investigation 
for which our tribute of gratitude is due 
first of all, to Robert Koch. 
If we review the results of our most 
recent investigations into the bacteria 
of the air, we find a conformity to exist 
throughout, and this conformity has 
greater significance in view of the vary- 
ing methods of investigation employed 
by the different observers. 
Practically every form of germ-life 
which we comprise under the common 
name micro-organisms, is found in the 
air to a widely varying extent of distri- 
bution ; bacilli, cocci, yeast fungi and 
schizomycetes are usually all present at 
the same time. As well in the extent 
of their dissemination as in their mul- 
tiplicity are there extreme variations, 
but these variations have a decided!}' 
peculiar similarity and are always de- 
pendent upon similar circumstances. 
For instance, in dwelling-houses, the 
schizomycetes, bacilli and cocci predom- 
inate over the mold fungi, while in the 
open atmosphere, more of the mold AIR !1d CONTACT INFECTION. 
spores are present. The number of 
germs varies from a few to many thou- 
sand per cubic centimeter. 
The air of large cities contains a 
greater number of bacteria than does 
country air, in damp weather the num- 
ber of bacteria in general is less than 
in dry weather, in winds greater num- 
bers are present than in still air. In 
the middle of the Atlantic Ocean, and 
upon mountains in the Alps range 
which are continuously covered with 
snow, the air is practically free from 
bacteria.* 
Land winds usually contain more 
bacteria than do sea winds ; for instance, 
the winds which blew from the land 
towards Catania as found by Condorelli- 
Mangere, always contained more bac- 
teria than the wind which blew from 
mid sea to Catania. The same condi- 
tions with reference to land and sea 
winds were found by Uffelmann in Ros- 
tock and Ciorgio Roster on the Island 
of Elba. 
Many of the older writers, for in- 
stance, Loewnhoek, we find to have 
maintained that all bacteria originated 
from the air and that from this source 
ORganic material is infected and its 
decomposition induced. The same line 
of thought also made itself very mani- 
fest in Lister’s first writings. With 
this opinion, i. e., that the air is the 
natural habitat of the micro-organisms, 
and that from this source organic mat- 
erial is infected secondarily, we must, 
with our present knowledge of the 
requirements of the bacteria for exist- 
ence, positively disagree. It is not 
the air which, par excellence, broods 
and harbors the deadly organisms and 
acts as the source of infection of every- 
thing else, the conditions are rather the 
reverse; it is in the organic material 
that the germs exist; only exceptionally 
do they from here gain entrance to the 
air. All the requirements for growth 
and multiplication of micro-organisms, 
viz. : warmth, moisture, and a nutrient 
media, are not present in the air, and, 
as for the schizomycetes, yeast fungi 
and mold spores, the air is anything 
but a favorable place of maintenance. 
Then there are bacteria, the so-called 
anaerobic organisms, which are antag- 
onized in their growth by the air as a 
gaseous medium—among this class we 
have the bacillus of tetanus to include 
— and there are presented by the air, 
especially by a clear atmosphere, a num- 
ber of factors, as dryness, diffused day- 
light and sunshine, which are now known 
to exert an unfavorable and directly 
damaging influence upon the micro- 
organisms. 
Only transitorily do germs gain en- 
trance to the air from their essential 
habitat, the warm, moist and organic 
material of the earth’s surface, and this 
furthermore under only one condition, 
i. e. when they are disseminated as dry 
dust. Naegeli, as early as the year 
1870, showed theoretically and experi- 
mentally, that the micro-organisms onty 
as dry dust can become mixed with the 
air, and that never do they gain en- 
trance to the latter from fluids. Yet 
even to-day it is difficult for an individ- 
ual who inhales the nauseous vapors of 
a decomposing fluid to reconcile him- 
self to the belief that with the fumes, 
♦Upon the fact of the absence of bacteria in 
the air of raid-ocean I convinced myself in a recent 
transatlantic voyage. While still in the harbor of 
Antwerp, bacilli were present in the air varying in 
number from three to five hundred per cubic meter, 
as determined by aspirating the air through large 
tubes. Sailing down the Schelda River the 
number decreased to two or three hundred, a >d in 
the North Sea almost no germs were present. Upon 
entering and sailing through the English Chauuei. 
the observations continued, revealed the presence of 
bacteria in the air varying from one to three hun- 
dred, percubic meter althoughin the widerparts of 
the Channel the number detected on exposed gela- 
tine and agar plates was much less. Beyoud the 
S jilly Islands the bacteria gradually diminished and 
in the Atlantic Ocean from five to forty degrees west 
longitu le no germs at all were present. FRANK J. THORNBUJ^. 
4 
germs from the contaminated fluid are 
not inhaled, not-with-standing that all 
investigations have proven the incor- 
rectness of this opinion. Air offensive 
in odor frequently contains fewer bac- 
teria than that which we inhale as pure 
and agreeable, and the stinking air of 
out-houses, sink holes and canals, has 
always been found purer bacteriologi- 
cally than the air of the streets, of 
dwelling-houses and of gardens. 
According to investigations made by 
Hesse and Petri, the open air in the 
interior of Berlin always contains from 
several hundred to one thousand bac- 
teria per cubic meter, and that of dwell- 
ing houses from six to ten thousand, 
while Petri alone found that the air in 
the canal below Potzdamer Place showed 
none at all, or only a few scattered 
germs. 
In fact, the air below Potzdamer 
Place is', bacteriologically, the purest 
in the whole city of Berlin, and even at 
the top of the Court House tower an 
individual would inhale a greater num- 
ber of germs, as here according to 
Hesse eight hundred per cubic meter 
are present. It has been experimen- 
tally proven that even through powerful 
current of air passed over the upper 
surface of fluids containing bacteria, 
germs are not disseminated, that is to 
sa}* the solution only is stirred up and 
then setlles, carrying down with it also 
the bacteria. 
The sun which pours its hot rays upon 
stagnant pools swarming in micro-or- 
ganisms, of course vaporizes the water 
and generates foul odors, but never are 
bacteria liberated from the solution, 
and even though the drops of rain and 
hail stones the size of a walnut which 
were showered over St. Petersburg in a 
storm, revealed the presence of bac- 
teria (Foutin), we are not to infer that 
these germs arose from the water as it 
evaporated, but that later the dust par- 
tides in the atmosphere became envel- 
oped by the precipitation. 
The presence of greater numbers of 
bacteria in dry and moving, than in 
moist air, is a sequence of the excessive 
circulation of dust which isinduced by 
dryness. The reason why there are 
fewer bacteria in the air after, than be- 
fore, a rain, is the fact that the water in 
falling carries down with it the germs, 
and especially explanatory is the satur- 
ation of the earth’s surface caused by a 
protracted rain, preventing temporarily 
the rising of dust. The absence, fur- 
thermore, of micro-organisms in the air 
upon icebergs and in mid-ocean, is due 
simply to the fact that here there is no 
dust containing bacteria which can be 
stirred up by the motion of the air, and 
that the glaciers as well as the sea 
water have the property of holding 
down the bacteria contained in them. 
Condorelli-Mangeri found in Catania, 
that during the great assemblage of 
the multitudes at the time of earth- 
quakes, the air contained more bacteria 
than otherwise. The air of stalls in 
which small animals are kept and move 
about, as for instance, in the pens in 
the Hygienic Institute, Berlin, is, ac- 
cording to Petri, very rich in germs; it 
contains upwards of thirty-four thou- 
sand bacteria and about seven thousand 
four huudred mold fungi per cubic 
meter. In the air of work shops the 
number of bacteria increases rapidly as 
soon as the work is begun, and in bar- 
racks, hospitals and dwellings, the 
number of bacteria in the air is found 
to be always greatest shortly after the 
rooms have been swept and dusted. 
In the operating room of the Billroth 
clinic, the number of bacteria in the air 
is always greatest while the clinic is in 
progress, after entrance of the students, 
and according to Hess the number of 
germs in the air of a school room in- 
creases from three thousand per cubic  CONTACT INFECTION. 
5 
meter to twenty thousand during the 
sessions and to forty thousand during 
the exit of the pupils. All these ob- 
servations only illustrate further the 
effect of the rising of dust on the bac- 
terial contents of the air. Very gen- 
eral in the medical profession as well as 
among the laity is the belief of the 
infectiousness of the breath, and this 
sentiment finds vivid expression in the 
fictitious narratives of very ancient 
times, which attributed to a vigorous 
exhalation of the monsters, the prop- 
erty of destroying everything it en- 
countered. It is surprising that at 
the beginning of the antiseptic era 
special importance was not attributed 
to expired air as a source of wound 
infection, for it is not difficult to under- 
stand, a priori, that from the views in 
vogue a variety of suspicions might 
have been formed by operators. 
Exact bacteriological study has, how- 
ever, dispersed these views, and even 
though the air of an over-crowded room 
rapidly deteriorates and becomes irres- 
pirable in the process of respiration, 
it is to be emphasized that germs, com- 
prising the bacilli and mold fungi, do 
not participate to any appreciable ex- 
tent in this deterioration, and that the 
latter, as in case of tunnels, pertains 
more especially to the gaseous constitu- 
tents. Since Tyndall discovered that 
the breath of man is entirely free from 
bacteria, a variety of investigations 
have been made into the exhaled air, 
and, concordantly, they have shown 
that micro-organisms instead of being 
given off from the respiratory tract are 
rather taken up from the air and fil- 
tered out. 
In the air of sick rooms very rich in 
bacteria, of six hundred germs inhaled, 
not more than one is found in the ex- 
haled air. Cadeac and Malet placed 
healthy sheep opposite to others affect- 
ed with anthrax and sheep pox and 
allowed them to breathe for long inter- 
vals through tubes 0.30 to 1.50 meters 
in length, varying tlieir experiments in 
a number of ways, but never were they 
successful in infecting through the 
breath of diseased animals, those which 
were healthy. The lungs do not give 
up bacteria from their moist alveolar 
surfaces but rather have an opposite 
effect, working as filters, and is it only 
possible for expired air to act in the 
transmission of germs when sputum, 
mucous secretion, or tissue shreds, are 
expelled from the expiratory tract in 
paroxysms of coughing. As correctly 
stated by Strauss the bacteria contained 
in the air of an over-crowded apart- 
ment must be diminished by the act of 
respiration, and it may be of consola- 
tion to a clinical lecturer, whose audi- 
torium becomes filled with listners, 
entering in the raising of dust, to know 
that each individual brings with him in 
the capacity of his lungs, a filter ap- 
paratus and that with each act of res- 
piration he renders about five hundred 
cubic centimeters of air free from germs. 
A surgeon need not fear that he will 
infect a wound with his breath, nor that 
a patient suffering from sepsis in the 
act of respiration can fill the air of a 
ward with infectious organisms. 
The more our bacteriological know- 
ledge has been extended, the more 
frequently the true source of bacteria 
has been investigated, and the more 
we have endeavored experimentally to 
transmit the wound diseases, so much 
the more have our fears of an infection 
through the air diminished, and so much 
the less appears to be the danger of 
disease being communicated in this way, 
as compared with that by direct con- 
tact of infectious materials. The simple 
consideration of the number of bacteria 
which can gain acces to a wound, on 
the one hand, through the air, and on 
the other hand through contact, is suffi- FRANK J. THORNBUrI^ 
cient to reduce our fears of the so- 
called air infection. It is true it 
appears large when we think of a cubic 
centimeter of air containing 1000 or 
indeed 20,000 or 40,000 germs, but what 
are these numbers as compared with 
the bacteria contained in decomposed 
organic materials. The Spree River 
water in Berlin, for instance, contains 
in each cubic centimeter, i. e., in the 
millionth part of the above quantity of 
air, as many thousands of bacteria, and 
the number of germs in a drop of pus 
or other extensively decomposed fluid 
•amounts to millions. Let us take to il- 
lustrate these proportions, a frequent 
instance in practice: The germs of 
the atmosphere which gain access to a 
wound settle upon it from air moder- 
ately in motion, by reason of gravity. 
By repeated investigations in the Von 
Bergmann clinic, we have proven, in 
the operating room with the auditorium 
occupied, that the number of bacteria 
which settle upon the surface of the 
wound a square decimeter in extent in 
the course of a half hour amounts to 
about 60 to 70 ; the number which de- 
posit from the open air in the vicinity 
of the clinic being, however, much in 
the decrease. 
The Spree River flows just past the 
clinic, and the number of bacteria which 
it here contains according to investiga- 
tion in the Hygienic Institute, varies 
from 3200 to 15,000 per cubic centime- 
ter; the average number is 37,525. Let 
us consider now the not infrequent in- 
stance of a ship hand on the Spree 
receiving a wound and suppose it 
happens to be a wound a square deci- 
meter in extent — the individual coming 
to the clinic with the wound open and 
undisturbed, although exposed to the 
action of the air, would receive upon 
its surface in the lapse of one half hour 
before application of the dressing, at 
most, from 60 to 70 germs which, fur- 
tliermore, are scattered loosely and very 
superficially over the blood clot. If, in 
accordance with the usual custom, the 
wound be now irrigated with a liter of 
Spree water, slowly and thoroughly for 
the purpose of cleansing it may readily 
be estimated that over 37,000,000 mi- 
cro-organisms would be brought in con- 
tact, and it defeats all efforts at calcula- 
tion as far as numbers of bacteria are 
concerned, when, in addition, the part 
is wrapped in a dirty cloth to which is 
adherent usually in mass decomposed 
material rich in bacteria. 
Lister was of the opinion that the 
bacteria of the air which produce 
changes and decomposition in organic 
substrata are also those which cause 
wound infection. Modern investiga- 
tion has long since demonstrated the 
incorrectness of this opinion, however, 
and shown that the germs of wound 
infection are entirely different from 
those of ordinary putrefaction scattered 
over the earth. The direct examination 
of the air for the now recognized cause 
of the wound-infection diseases in man, 
has afforded very scant, and for the 
most part only negative, evidence. 
By far the greater number of air 
fungi belong to the innocent germs—the 
mold spores, yeast plants, and fission 
fungi, which, for man, are not patho- 
genic. And when the germs of wound 
infection have been found in the air, 
as in hospitals, they have, as compared 
with other micro-organisms, been great- 
ly in the minority, and we find as the 
result of all our investigations, that the 
air which is inherently an unfavorable 
abode for micro-organisms, allows the 
bacteria of wound infection, which un- 
avoidably gain access to it, to die very 
suddenly. 
Thus gradually the theories in vogue 
have been forced to decline, success- 
ively, in advance of accurate investiga- 
tion, and of the original views of Lister AIR! AND CONTACT INFECTION. 
regarding the importance of the bacteria 
of the air in wound infection, almost 
nothing remains. In practice, however, 
there had been experienced by Lister’s 
original views what frequently occurs in 
case of greatly inaugurated ideas when 
put into practical application. Unin- 
fluenced by the manner and complicacy 
with which the method was presented 
as an established requirement, the good 
and truth have crystallized out, the non- 
essential and superfluous have volunta- 
rily remained behind. Thus prior to the 
evidence afforded through experimental 
bacteriology, the importance to the 
physician of air infection had greatly 
diminished, and from year to year in- 
creased stress came to be laid upon con- 
tact infection in the avoidance of wound 
diseases. With timidity, first one oper- 
ator and then another omitted the use 
of the spray, and then everywhere it 
rapidly disappeared, because experience 
very clearly demonstrated that it was 
unnecessary. 
So, also, will it occur with wound 
irrigation recommended by Lister for 
the destruction of infectious germs 
unavoidably gaining entrance to the 
wound through the air, and which after 
discontinuance of the spray by numer- 
ous operators, were given increased 
emphasis as a substitute for the spray. 
The results in wound repair which 
Von Bergmann has attained for years 
in his clinic wdthout irrigation, and the 
results which have been attained in the 
same manner by others who have imit- 
ated his example, are plain evidence that 
antiseptic wound irrigation does not 
belong to the true character of modern 
teaching and is only an unnecessary 
evil. It is not required that we should 
fill the air of a room with carbolic vapor, 
we have no occasion to have filtered or 
heated air poured into the room through 
ventilators, nor is it necessary that 
we should deluge our fresh operation 
wouuds with antiseptic agents. We 
attain favorable resalts without all these. 
The individual operating room of the 
Bergmann clinic is a polygonal building 
enclosing an amphitheatre constructed 
of wood which at each clinic hour is filled 
with several hundred students. Large 
curtains suspended from the ceiling shut 
off the sun on one side; a profuse 
Arabesque lattice work covers a portion 
of the rear wall of the room, and just 
over the heads of the operators upon 
ornamental socles are placed the busts 
of Von Bergmann’s three celebrated 
predecessors. Still, no one would con- 
tend that in these rooms the conditions 
would be especially contrary to the 
aggregation of dust, and repeated ex- 
aminations have shown us that its air 
contains more bacteria than the air of 
any other room in the clinic, yet, not- 
withstanding, all operations here per- 
formed are attended with as favorable 
results as could be desired. In this air 
the abdominal cavity is quietly opened 
and major amputations are performed, 
pauses are made during the operation, 
the wounds openly demonstrated to the 
students, and then simply sutured, 
and in no instance has injury been seen 
to result from too long exposure to the 
atmosphere. 
The individual precaution which we 
are required to observe against a possi- 
ble infection through the air is the 
avoidance of the excessive clouding of 
dust. We would not be justified in 
operating where quantities of dust and 
dirt are blowing about and can en- 
counter the region of the operation; 
this requirement, in the operating room, 
is very easily fulfilled, and affords dif- 
ficulty only in the open air. It is also 
well not to clean up a room or to sweep 
just before a major operation, as we 
have seen that in this way dust 
always becomes agitated. Further to 
be observed is especial precaution in FRANK J. THORNBU •« 
the handling of dressings saturated with 
pus. That the spray does not exert a 
favorable influence over the bacterial 
contents of the air attributed to it by 
Lister, is conclusively demonstrated. 
According to the investigations of Stern, 
the purifying action possessed by the 
spray is very unimportant; so also, is 
it impossible by the ordinary ventilation 
and airing of a room to effectually dimin- 
ish the bacteria contained in it. Investi- 
gations by Stern showed that after arti- 
ficial dissemination of bacteria, those 
which are heavier gravitate to the sur- 
face in the course of one-half an hour 
and the air becomes free from germs, 
while in case of wool and rag dust, as 
also with mold spores, a somewhat 
longer time is required. The most 
effectual means of freeing the air of a 
room from its bacteria is to keep the 
room closed for a number of hours until 
the germs have settled to the floor. 
Then we have done all that we are 
required to do in the avoidance of an 
infection of wounds through the air. 
All our further efforts are to be di- 
rected against contact infection.