GRADUAL DEVELOPMENT OF THE GERM THEORY. 73 



Some investigators asserted that in spite of the most 

 careful isolation of the fermentescible substances, and m 

 spite of the most thorough destruction of existing germs, 

 putrefaction and fermentation nevertheless occurred. 

 These experiments will he discussed helow, hut I may 

 here point out that a contradictory result must be 

 obtained when even one of the many necessary precau- 

 tions is omitted during the experiment, and that 

 therefore a certain percentage of unsuccessful attempts 

 at preservation is something quite intelligible. 



The more experienced the experimenter, the more 

 rarely do the experiments fail ; the more the methods of 

 preserving food have been developed, so much the more 

 successful are the results. The best experimenter must 

 register a series of failures when he begins to busy him- 

 self with these questions, in which the sources of error 

 are so numerous, and in which unusual precautions are 

 required. But for this very reason a few of these con- 

 tradictory experiments, in which putrefaction and fermen- 

 tation occurred, in spite of the apparently complete 

 exclusion of all germs, cannot be used as a proof against 

 the vitalistic theory. 



If we assume, for the present, that the result of the 

 most numerous and carefully conducted of these experi- 

 ments is that by the exclusion of organisms putrefaction 

 and fermentation are prevented in fermentescible sub- 

 stances, there at once arises another old matter of dis- 

 pute, namely, that with regard to abiogenesis (generatio 

 (equivoca). Seeing that no development of organisms 

 occurs in substances which under ordinary conditions 

 offer a most admirable soil for their development, when 

 the access of living organisms is rendered impossible, 

 and seeing that the most active life at once appears as 

 soon as even the smallest number of living organisms 

 enters, tha conclusion is justified that the living cells 

 cannot be formed from unorganised material, but that 

 they always originate from another organised cell. 



The experiments referred to admitted, however, of 

 two valid objections, and hence they required to be 

 further modified if they were to prove absolutely the 



