380 THE BEGINNINGS OF LIFE. 



the one hand, that the living things met with derived 

 their origin from pre-existing 'germs' that had survived 

 all the destructive conditions to which the media sup- 

 posed to contain them had been subjected ; whilst, on 

 the other hand, it was contended that if the media had 

 been subjected to conditions which (by evidence the 

 most direct and positive) had been shown to be de- 

 structive to the lowest living things, then any such living 

 things as were subsequently discovered in these fluids 

 must have been evolved de novo. It was a question, 

 therefore, on the one hand, as to the degree of c vital 

 resistance' to heat which might be displayed by the 

 lowest living things; and on the other, as to the 

 strength of the tendency in the organic matter of the 

 solution to undergo changes of a fermentative cha- 

 racter, coupled with the degree to which this molecular 

 mobility could persist in spite of the disruptive agency 

 of the heat to which the organic matter had been 

 subjected. Whatever fluids are employed, if after they 

 have been boiled and exposed to a given set of con- 

 ditions, organisms are not found, their absence is 

 explicable in one of two ways that is, in accordance 

 with either of the two opposing views. Either the heat 

 has proved destructive to all living things in the solu- 

 tions; or else the restrictive conditions to which the 

 organic matter in these solutions has been exposed have 

 been such as to prevent the occurrence of fermentative 

 changes. Any person seriously wishing to ascertain the 

 truth, and competent to deal with such a subject, of 



