VITALITY OF PUTEEFACTIVE OKGANISMS. 221 



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 nutritive liquid 

 an infinitesimal residue of oxygen can develop a sensible 

 amount of life. I may add that I have tested the ex- 

 haustion 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 prin- 

 ciple 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. Tt 

 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 in- 

 fusions pellucid for an indefinite time in vessels purged 

 of air by boiling and properly sealed. I will give a few 



' 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. 



