53 



Flasks thus prepared were maintained at a warmth vary- 

 ing from 50° to 90"" Fahr. for long periods — many weeks 

 and months — some in the dark and some exposed to the 

 light, with the following results. 



I. Simple filtered infusions of animal or vegetable tissues 

 — a very considerable variety were tried — boiled over the 

 flame for five or ten minutes, in flasks previously plugged 

 with cotton wool, remained permanently barren. This 

 result was absolutely invariable. 



II. More complex mixtures — milk, neutralized or alkalized 

 infusions of vegetable and animal tissues, similar albuminous 

 and gelatinous solutions, mixtures containing fragments of 

 animal or vegetable substances or cheese — yielded variable 

 results. In none of them did fungoid growths make their 

 appearance — but monads and bacteria frequently appeared 

 in abundance. 



This seemingly contradictory result was inferred to be 

 due to the ineffective application of the heat in the process 

 of direct boiling over a flame. It was found that many of 

 these more complex mixtures frothed excessively when 

 boiled — brisk ebullition could not therefore be maintained 

 — particles were spurted about on the sides of the flask, and, 

 in this way, apparently escaped effective exposure to the 

 heat. Even when the boiling was prolonged for 20 or 30 

 minutes the results were still uncertain — sometimes the 

 flasks remained barren — sometimes they became turbid 

 and swarmed with bacteria. 



III. By the second modification of the experiment much 

 more constant results were obtained — the flasks remained 

 almost always permanently barren — and the few exceptions 

 were found to be due to some imperfection in the conduct of 



