162 
PEOFESSOE TYNDALL ON THE DEPOETMENT AND VITAL 
more deep than that of the acidulated water. The alkaline and distilled-water 
infusions emitted a rich odour of hay, while the smell of the acid infusion was very 
faint, and not like that of hay. The hay was permitted to soak from the 8th to the 
11th of November. It was then digested for three hours in the same liquid at a tempe- 
rature of 120° F., boiled, filtered, and introduced into the closed chambers, where it was 
reboiled in each case for five minutes. 
Prior to digesting the hay in the liquid in which it had been soaked Bacteria had deve- 
loped in swarms. These, of course, were killed by the boiling, and they were not entirely 
removed by the filtration. The alkaline infusion, indeed, though filtered repeatedly, was 
sufficiently turbid to prevent the flame of a candle placed behind the tubes containing 
it from being seen. The same to a less extent was true of the distilled-water infusion. 
This latter had been divided into two portions, one of which was accurately neutralized, 
and the other left unneutralized, separate chambers being devoted to each. 
From the 11th to the 18th of November the only change observed in any of the 
infusions was in the direction of increased transparency. They all became clearer with 
time, the distilled-water infusions becoming particularly clear and brilliant at the top. 
After two or three days’ quiet the alkaline infusion allowed a flame placed behind it to 
be seen of a deep and brilliant red. The acidulated-water infusion remained entirely 
unchanged ; but this is not worth dwelling on, for in this case, even when exposed to 
the common air, the infusion resisted infection for a considerable time. 
In no case was the fatty scum which had been already so frequently observed formed 
in any one of the tubes. Some change inimical to the particular organisms which produce 
this scum must have been caused by the soaking of the hay. 
Examined microscopically on the 18th of November these infusions, I thought, 
exhibited undoubted evidences of Bacterial life. Bacterial forms were unquestionably 
there in considerable numbers, more particularly in the sediment at the bottoms of the 
tubes. Nor do I now see any valid grounds for doubting the presence of life ; but I 
was warned against drawing too hastily the conclusion which first prompted itself, by 
boiling an infusion swarming with active Bacteria , and submitting the liquid after 
cooling to microscopic examination. Plere also the dead Bacterial forms were preserved, 
and it was extremely difficult to distinguish their motions, which were certainly Brownian 
motions, from those observed in the protected infusions of soaked hay. 
The experiment was thought worth repeating. On the 16th of November accord- 
ingly chopped bundles of old Heathfield hay and new Heathfield hay, and of 
old London hay and new London hay, were placed in glass dishes containing dis- 
tilled water, and were thus soaked until the 18th. They were then moved from 
the lower laboratory, and taken, with their glass covers, to a distant room at the 
top of the Royal Institution. Here the four specimens of hay were digested for three 
hours at a temperature of 120° Fahr. They were filtered, boiled, refiltered, some of 
them through 100 layers of filter-paper; after which they were introduced into four 
closed chambers of six tubes each, and then boiled for five minutes. 
