APPENDIX. 325 



melon, beetroot and artichoke, for example, whose parasitic 

 or epiphytic germs were unlikely to have suffered desic- 

 cation. 



Boiled for periods varying from five to fifteen minutes 

 and exposed afterwards to moteless air, in numberless 

 experiments these infusions broke down, charging^them- 

 selves throughout with organisms, and loading themselves, 

 almost in all cases, with a soapy corrugated scum. 



I then fell back upon infusions whose deportment had 

 been previously familiar to me, and in the sterilization of 

 which I had never experienced any difl&culty. Fish, flesh, 

 and vegetables were re-subjected to trial. Though the pre- 

 cautions taken to avoid contamination were far more 

 stringent than those observed in my first inquiry, and 

 though the interval of boiling was sometimes tripled in 

 duration, these infusions, in almost every instance, broke 

 down. Spontaneously purified air, filtered air, and calcined 

 air (calcined, I may add, with far greater severity than 

 was found necessary a year previously) failed, in almost 

 all cases, to protect the infusions from putrefaction. 



I was sometimes cheered by a success which, at the 

 time of its occurrence, would seem to be the result of 

 increased severity in the methods of experiment. But the 

 success was subsequently so opposed by failure that it 

 finally stood out rather as an accident than as the normal 

 result of the inquiry. 



I had the most implicit confidence in the correctness of 

 my earlier experiments ; indeed incorrectness would have 

 led to consequences exactly opposite to those arrived at. 

 Errors of manipulation would have filled my tubes and 

 flasks with organisms, instead of leaving them transparent 

 a,nd void of life. By the unsuccessful experiments above 

 referred to a clear issue was therefore raised: — Either 

 infusions of fish, flesh and vegetables had become endowed 

 in 1876 with an inherent generative energy which they did 

 not possess in 1875, or some new contagium external to the 

 infusions, and of a far more obstinate character than that 

 of 1875, had been brought to bear upon them at the later 



