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PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
and left unboiled 1 Probably with sufficiently perfect exhaustion all infusions would be 
sterilized. But in the trials I have thus far made some of the unboiled infusions have 
become cloudy, while others have remained clear. Thus three bulbs of mutton-infusion 
exhausted for four hours, two bulbs of beef-infusion exhausted for three hours, four 
bulbs of pork-infusion exhausted for four hours and left unboiled remain as transparent 
and as free from life as their boiled companions. Various other instances of sterilization 
without boiling might be cited. On the other hand, three bulbs of neutralized urine, 
exhausted for five hours and left unboiled, became cloudy. A case of cucumber-infusion 
which behaved similarly has been cited above. It is difficult, if not impossible, to remove 
from the infusion and the space above it the last traces of air ; and when backed by a 
highly neutritive liquid an infinitesimal residue of oxygen can develop a sensible amount 
of life. I may add that 1 have tested the exhaustion of some of the cloudy bulbs, and 
have found it in every case defective. 
The foregoing instances sufficiently illustrate the dependence of the organisms here 
under review upon the supply of oxygen*. I think it probable that the principle thus 
indicated is capable of useful and extensive practical application. 
§ 24. Mortality of Germs through defect of Oxygen consequent on boiling the Infusion. 
Long prior to these experiments with the Sprengel pump, the influence of atmospheric 
oxygen on the life of these organisms had been brought home to me. It revealed itself 
in a striking manner in experiments with infusions purged of air by boiling, the vessels 
containing them being carefully sealed during ebullition. At a time when the 
atmosphere of our laboratory was so laden with infection that no escape for animal or 
vegetable liquids introduced in the usual way into closed chambers was possible, it was 
perfectly easy to keep the same infusions pellucid for an indefinite time in vessels purged 
of air by boiling and properly sealed. I will give a few out of the multitude of examples 
that might be cited in proof of this statement. 
On the 2nd of October fourteen of our ordinary retort-flasks (fig. 4) were charged with 
a neutralized infusion of hay. They were boiled for three minutes in an oil-bath, and 
hermetically sealed whilst boiling. Thirteen out of the fourteen tubes remained per- 
fectly barren, retaining for months their pristine colour and transparency. 
On the 18th of November six retort-flasks were filled with turnip-, five with cucumber-, 
five with beetroot-, and four with parsnep-infusion. The six turnip-flasks remained per- 
manently pellucid, yielding a clear water-hammer ring. The five beetroot-flasks remained 
also permanently barren, all yielding the water-hammer sound. Of the parsnep-flasks, 
two became turbid, but two remained clear. Of the cucumber-flasks, three became 
cloudy, while three remained permanently clear. Neither in the case of the parsnep 
* In search of this gas they sometimes rise into the liquid film which covers the interior of the bulb to the 
height of an inch and more above the surface of the liquid, forming within the bulb a gauzy scum which 
appears as if lifted by capillary attraction. Their mode of nutrition must therefore be very different from that 
of Torula- cells, as revealed by the excellent researches of Pasteur. 
