ApriL 8, 1915] 


(2) It is caused by the growth of micro-organisms 
and does not occur independently of them. 
(3) he micro-organisms that produce fermentation 
and putrefaction are conveyed by the air on the dust 
that floats in it. : 
(4) These micro-organisms can be destroyed by heat 
and other agencies, or separated by filtration. 
(5) Certain recognisable organisms produce definite 
and distinct fermentative processes. 
(6) All of these organisms require oxygen. Some 
of them flourish only in the presence of tree oxygen 
(aerobic), others only in its absence (anaerobic). The 
latter acquire their oxygen from the bodies which, by 
their growth, they are causing to ferment or putrefy. 
(7) Many natural animal and vegetable products 
have no tendency to ferment or putrefy even in the 
presence of oxygen, if collected with proper precautions 
and kept in sterilised vessels. 
(8) Spontaneous generation has never been observed 
to occur, and thus may be regarded as a chimera. 
Now it will be observed that Pasteur’s worl pre- 
sented Lister with two great fundamental facts. 
(1) That putrefaction is caused by germs which can 
be destroyed by heat and chemicals and separated by 
filtration. 
(2) That germs are carried by the dust in the air. 
It is true that both Pasteur and Lister did not fail 
to recognise that if the air carried the germs it must 
deposit them upon the surface of everything, and that 
therefore the surface of every solid and the whole of 
every liquid must be, or might be, infectious. It is 
also true that Lister bore this in mind, and acted on 
the assumption that it was true from the very first. 
But still it was the air to which he paid and directed 
most attention—more attention, as we shall see, than 
it deserved. He probably did not recognise, he cer- 
tainly did not say, that his precautions with regard to 
other sources of infection were far more important 
than those which he took with regard to infection 
from the air. 
The sceptics and cavillers, the believers in spon- 
taneous generation, kept saying, ‘‘Show us your germs 
in the air.” They did not doubt that organisms were 
found in putrefying substances, they could not do 
that; but they said that they might be accidental, the 
result of putrefaction, not the cause of it, and asked 
for proof that germs existed in the air. Pasteur had 
tried to meet this objection by filtering the air through 
gun-cotton, which he afterwards dissolved and sub- 
mitted the solution to the microscope. There were 
certainly objects which he was satisfied were germs, 
but the doubters were still unconvinced. 
A few years later, about 1869, John Tyndall, whose 
eloquent addresses on ‘‘ Dust and Disease ” were listened 
to with breathless attention in this hall, succeeded in 
showing to the naked eye of untrained amateurs, the 
existence of, and the amount of, floating dust in any 
given sample of air, by passing through it a concen- 
trated beam of light. Next he showed that, if the 
air was left undisturbed, say in a glass flask, the dust 
settled, and there was nothing for the beam to illu- 
minate. Then he produced the same result by filter- 
ing the air, or by raising to a great heat a piece of 
platinum wire passing through the flask which burned 
up the dust. Finally, he proved, by a series of charm- 
ingly simple experiments, that what he called optically 
pure air was incapable of setting up decomposition 
in putrescible fluids, whereas optically impure air 
invariably caused them to decompose. 
Most of these facts were known to Lister in 1865. 
All the evidence pointed in the same direction; and 
therefore, stated in the simplest way, the problem 
seemed to be to kill the germs which might have 
gained access to the wound before it came under 
NO. 2371, VOL. 95] 
NATURE 

161 

treatment, and to prevent the air from carrying in 
others afterwards. 
He first applied what he now called the antiseptic 
principle to compound fractures, injuries which, above 
all others, were liable to be followed by those hospital 
plagues—pyemia, erysipelas, and hospital gangrene. 
He had to choose between the three recognised 
methods of excluding the germs—filtration, calcining, 
and chemical antiseptics—and he naturally selected 
the last as the most convenient. The first antiseptic 
he tried was carbolic acid, and as the crude sample 
he first worked with was insoluble in water he used 
it undiluted. 
His plan for treating compound fractures was, after 
cleansing the wound, to sponge the whole of the raw 
surface with this undiluted crude German creosote in 
order to destroy the germs introduced by dirt or other 
foreign material at the time of the accident, or that, 
as he supposed, had been carried to it by the air. 
The carbolic acid mixed with the blood, caused an 
antiseptic crust, which he fortified by covering it 
with a thin piece of block-tin, and this crust effectually 
prevented the access of unpurified air to the wound; 
for he left it undisturbed for days or weeks and 
painted the outside with more of the undiluted acid 
from time to time. 
I wish to impress upon you that in the earliest 
dressings he used a very strong antiseptic and did 
his best absolutely to exclude the air, and it is im- 
portant to note that his results were strikingly good, 
in spite of the fact that the undiluted acid did actually 
cause a certain amount of superficial sloughing—or 
death of the tissues—in the parts to which it was 
applied. As time went on a purer carbolic acid was 
obtained which dissolved in water, so he abandoned 
the caustic undiluted acid in favour of a saturated 
watery solution: 1 part to 20. 
He soon extended the treatment, first to abscesses 
and then to ordinary operation wounds. The old 
antiseptic crust was soon given up, and various dress- 
ings containing carbolic acid or other antiseptics were 
employed instead. But for a long time he was so 
anxious about the air that he irrigated the wound 
with a solution of carbolic acid in water throughout 
an operation, and took the most elaborate precautions 
against allowing any aii that had not been submitted 
to the influence of carbolic acid to reach the wound 
at the changing of the dressings. He used to say 
that merely taking out a drainage tube without anti- 
septic precautions involved a serious risk, because the 
air which rushed in to take its place might carry some 
speck of dust and a germ along with it. 
In his most palmy days, when he was professor of 
clinical surgery at Edinburgh (1869-77), and Edin- 
burgh was for the time the surgeon’s Mecca, he intro- 
duced the spray in order to deal still more effectually 
with the air. In its most highly developed form the 
steam spray-producer threw a copious vapour, which 
was supposed to contain one part of carbolic acid in 
forty of water, that surrounded the whole region of the 
operation, and, if the room were small, might even 
fill the whole apartment with a pungent vapour, to 
the great discomfort of all concerned. He thought at 
the time that the momentary contact of the dust with 
the particles of carbolised water in the spray, or the 
carbolised atmosphere between the drops would be 
enough to destroy the germs; but in after years he 
owned that such a result was impossible. 
At this period, though he was still using strong 
antiseptic lotions very freely, his results were yet more 
remarkable; and in the meantime, relying on the anti- 
septic principle, he was doing new operations which, 
without it, he would have considered to be altogether 
unjustifiable. 
