206 
PKOE. TYNDALL ON PITTKEEACTIVE AND INEECTIYE OEOANISMS. 
result of the experiment was, that out of the fifty-seven tubes twenty-seven became 
turbid in a few days, while thirty remained for months without sensible alteration*. 
A considerable number of retort-flasks were charged at the same time with the same 
infusions, and boiled for five minutes in an oil-bath. The great majority of these 
flasks remained perfectly intact. 
Here, then, as elsewhere, the ground on which the doctrine of spontaneous genera- 
tion has sought to plant itself slips from under it ; for assuredly the scientific mind will 
attribute to other causes than to it the production of organisms in the minority of cases 
above referred to. 
One likely cause may here be signalized and illustrated. The experiments of Spal- 
lanzani on the action of heat upon seeds are well known, and they have been frequently 
cited by Dr. Bastian in support of his favourite thesis that the briefest exposure to the 
temperature of 212°Fahr. suffices to destroy all living matter. I have repeated many 
of Spallanzani’s experiments, and will here briefly refer to one series which bear upon 
the present point. Peas, kidney-beans, cress- and mustard-seed were tied up in small 
calico bags, and boiled for intervals varying from half a minute to five minutes. They 
were then carefully sown in flower-pots filled with well-prepared earth, and placed in a 
shed kept at a temperature of 7 0° Fahr. An unboiled sample of every seed was sown at 
the same time beside the boiled ones. The unboiled seeds sprouted vigorously. Thirty 
seconds’ exposure to the boiling temperature deprived both the peas and the beans of 
their power of germination. A few of the cress-seeds exposed for this interval sprouted, 
but the majority were killed, and all were killed by a minute’s boiling. On the other 
hand, a very large proportion of the mustard-seeds boiled for thirty seconds germinated. 
The time of exposure in the case of this seed was doubled, trebled, and quadrupled, 
leaving still a residue of life. The fertile mustard-seeds gradually diminished in number 
as the time of boiling increased, but even after two minutes’ boiling many of them 
germinated. 
And now comes a fact which I deem of some importance as regards the present inquiry. 
When the calico bag was abandoned, and the mustard-seeds were placed loosely in 
water, so as to ensure not only the free communication to them of its temperature, but 
free diffusion between the soluble portions of the seeds and the surrounding liquid, not 
one of them escaped the ordeal of thirty seconds’ boiling. In the first series of experi- 
ments, the bag which held the seeds together not only exercised a protecting influence 
itself, but it enabled the outside seeds to act as shields to the inside ones. Assuredly 
in a far higher degree will cheese shield germs contained within it. Unlike fruit and 
meat it is highly impervious to water. It thus wards off the liquid on which the softening 
and swelling of the germ depend, so that within such a substance the life of a germ might 
he indefinitely prolonged. 
* These chambers were prepared and their tubes charged prior to the introduction of hay into our labora- 
tory last autumn, otherwise the immunity of a single one of them could not have been secured. The chambers 
employed had stood over from my last investigation, and no pains had been taken to render them air-tight. 
