THE BEGINNINGS OF LIFE. 35 



'vacuo } whilst a similar solution which has been boiled 

 for some minutes does not at all readily become turbid 

 even when exposed to the air, although it will do so in 

 a few hours if some living Bacteria be purposely added. 

 Such facts seem to show, not only that living Bacteria 

 are scarce in the air, but also — from the fact that the 

 unboiled solution will rapidly become turbid — that the 

 solution originally contained some ferment whose 

 virtues were to a certain extent destroyed by the heat^. 

 Destroyed, however, only to a certain extent — since 

 the ammonic tartrate and sodic phosphate solution 

 which will no longer become turbid from presence of 

 Bacteria^ will, after a long period, yield Torula or one 

 of the simplest kinds of Fungi^, Destroyed only to a 

 certain extent also, because the citrate of iron and 

 ammonia solution will even yield Bacteria in addition 

 to other organisms, after an exposure to a temperature 

 of 145° C, and the solution of ammonic carbonate will 

 also yield Bacteria after an exposure to a still higher 

 temperature for a longer period. Thus the saline solu- 

 tions employed have, perhaps, needed the presence of 

 more unstable matter which might act the part of a 

 ferment, before life-giving changes could be initiated. 



However difficult it may be, at first, to imagine 

 that living things are capable of springing up de novo 

 in a solution of tartrate of ammonia and phosphate of 



^ The ferment must have been originally either in the water, in the 

 crystals, or in both. 

 2 See Appendix A, pp. i. and ii. 



D 2, 



