150 
PEOEESSOE TYNDALL ON THE DEPOETMENT AND VITAL 
tubes, its side windows w w, its pipette C, and its bent tubes a b, which connect the air 
of the chamber with the external air. 
In upwards of fifty chambers thus constructed, many of them used more than once, it 
was, without exception, proved that the sterilized infusion in contact with air shown to 
be self-cleansed by the luminous beam remained sterile. Never, in a single unexplained 
instance, did such an infusion show any signs of life. That the observed sterility was not 
due to any lack of nutritive power in the infusion, was proved by opening the back door 
and permitting the uncleansed air to enter the chamber. The contact of the floating 
matter with the infusions was invariably followed by the development of life. Numerous 
examples of these results were placed before the Fellows of the Royal Society at their 
Meeting on the 13th of January, 1876. 
Prior to the date here referred to, great public interest had been excited, and, I may 
add, considerable scientific uncertainty had been produced in reference to this subject, 
both in England and America, by the writings of Dr. Bastian. These writings consisted, 
in part, of theoretic considerations and reflections, not new, but sometimes very ably 
stated, based on the general doctrine of Evolution, and, in part, of very pungent criti- 
cisms of those who, though believers in Evolution, declined to accept the writer’s 
programme of its operations*. Passing over both theory and criticism, I thought it 
wise to fix upon certain well-defined statements of fact which lay at the basis of the 
weighty superstructure raised by their author, and to bring these statements to the test 
of strict experiment. 
Thus it was affirmed “ that boiled turnip- or hay-infusions exposed to ordinary air, 
exposed to filtered air, to calcined air, or shut off altogether from contact with air, are 
more or less prone to swarm with Bacteria and Vibriones in the course of from two 
to six days”f. I resorted accordingly to filtered air, calcined air, and to infusions with- 
drawn from air, but failed to discover the alleged “ proneness ” to run into living forms. 
It had also been affirmed that infusions of muscle, kidney, or liver, placed “ in a flask 
whose neck is drawn out and narrowed in the blowpipe flame, boiled, sealed during 
ebullition, and kept in a warm place, swarmed after a variable time with Bacteria 
and allied organisms I resorted to such flasks, employing infusions of fish, flesh, 
fowl, and viscera, and on the 13th of January was able to place before the Royal 
Society one hundred and thirty of them, every one of which negatived the foregoing 
statement. 
Two objections were subsequently urged against these results. The infusions, it was 
contended, were not sufficiently concentrated, nor were the temperatures sufficiently high. 
Both these objections were met by the statement that forty-eight hours’ exposure under 
the same circumstances to common air sufficed to fill these same infusions with life. 
Beyond this, however, I was able to show that the temperatures employed by me were 
exactly those which had previously been found most effectual by the writer who urged 
* See ‘Evolution, or the Origin of Life,’ pp. 168, 169. + Evolution, p. 94. 
+ Transactions of the Pathological Society, 1875, p. 272. 
