Infectious Diseases, Professor Tyndall paid a high compliment to the
lecturer for the thoroughly sound instruction which he had so clearly
conveyed. He had made it plain that contagion consisted, not of gas or
vapour, but of definite particles, sometimes floating in gas, in the
air we breathed, or in the water we drank; and that, like organic seeds
in the soil, they multiplied themselves indefinitely in suitable media,
the great probability being that these disease-producing particles
were living things. A close study of the subject, extending now over
several years, enabled him to agree entirely with the lecturer in the
parallelism which he had declared to exist between the phenomena of
contagious disease and the phenomena of ordinary putrefaction. The
case of flies, for example, to which the lecturer ascribed the power
of communicating disease from one person to another, was exactly
paralleled by phenomena in putrefaction. Chop up a beefsteak, steep it
in water, raise the temperature a little above the temperature of the
blood, pour off the water, and filter it; you get a perfectly clear
liquid; but that liquid placed in a bottle and exposed to the air soon
begins to get turbid, and that turbid liquid, under the microscope,
is found to be swarming with living organisms. By suitably heating
this perfectly clear beef-tea, it can be sterilised, everything being
killed which is capable of generating those little organisms which
produce the turbidity; and by keeping it from coming in contact with
the floating particles of the air, it might be preserved transparent
for years. He had now some sterilised beef-tea of this sort which had
been preserved for eighteen months in a state of perfect transparency.
But if a fly dipped its foot into an adjacent vessel containing
some of the turbid fluid, and then into the transparent fluid, that
contact would be sufficient to infect the sterilised infusion. In
forty-eight hours the clear liquid would be swarming with these
living organisms. The quantity of the turbid liquid which attaches
itself to the finest needle-point suffices to infect any amount of
the infusion, just as the vaccine lymph taken up on the point of a
surgeon's lancet spreads disease through the whole body. Here, also, as
in the case of contagious disease, there was a period of incubation.
In proof of what the lecturer had stated that the contagion of these
communicable diseases was not gaseous or liquid, but solid particles,
he would describe an experiment he had made only a few weeks since.
Eighteen months ago he had a chamber prepared from which all floating
particles of dust were removed, and in it he placed a number of
vessels containing animal and vegetable refuse which soon fell into
putrefaction, and also two or three vessels containing perfectly
clear beef-tea and mutton-broth, as transparent as water, in which
the infective particles had been killed by heat. Although all these
vessels had stood for eighteen months side by side there had been no
communication of contagion from one to the other. The beef-tea and
mutton-broth remained as transparent as when put in, though the other
vessels emitted a most noisome stench. But if a bubble were produced in
one of the putrefying masses by blowing into it, and if on rising to
the surface and bursting, the spray of the bubble was allowed to fall
into the transparent beef-tea or mutton-broth, in two days it became as
bad as its neighbours.
'Referring to another point on which the lecturer had insisted--namely,
that there was no power of spontaneous generation of the germs or
contagion of diseases, Professor Tyndall said that, though at present
great names were opposed to that view, he would venture to predict that
ten years hence there would be very few great names opposed to the
lecturer on that matter. With regard to the power of specific contagia
to be generated in decomposing animal matter, he would say that for the
last twenty-one years he had been in the habit of visiting the upper
Alpine valleys, where, amongst the Swiss châlets, there was the most
abominable decomposition going on from day to day, and exceedingly bad
smells, but there these contagious diseases were entirely unknown. If,
however, a person suffering from typhoid fever were transported there,
the disease would spread like wildfire from this infected focus, and
probably take possession of the entire population. It might be taken,
therefore, that any of these special diseases required its special
germ or seed for its production, just as you required a grape-seed
to produce a vine. He entirely agreed with all that Dr Corfield had
stated as to these diseases 'breeding true.' He never found the virus
of small-pox producing typhoid, or _vice versâ_. The subject was one of
the most important which could engage the attention of the scientific
physician.'
* * * * *
Printed and Published by W. & R. CHAMBERS, 47 Paternoster Row, LONDON,
and 339 High Street, EDINBURGH.
* * * * *
_All Rights Reserved._
* * * * *
Transcriber's note--the following changes have been made to this text:
Page 554: Milwaukie to Milwaukee
Page 558: tomatos to tomatoes