CHAPTER VIII. 



THE LIMITS OF 'VITAL RESISTANCE* TO HEAT. 



Conflicting analogies bearing on the question of the Origin of Life. 

 Views on this subject likely to be influenced by wider philosophical 

 beliefs. Physical theories of Life quite harmonious with possibility 

 of de novo origin. Both crystalline and living matter may be 

 . supposed to originate by same laws as determine their growth. 

 Whether this does occur with living matter has to be determined 

 by experiment. Only one mode of solving the problem. Import- 

 ance of ascertaining limits of ' vital resistance ' to Heat. Previously- 

 existing evidence on this subject. Limits in dry air, and limits in 

 water. General unanimity as to destructive influence of boiling 

 water. Observations of Pouchet, Meunier, Wyman, and Liebig 

 upon the effect of lower temperatures. Brownian and languid vital 

 movements. Their significance and meaning. Occurrence of re- 

 production the surest test that Bacteria are living. New experiments 

 with inoculated ammoniacal solutions. Show that Bacteria, Torulae, 

 and their germs are killed in fluids which have been raised to 

 140 F. Or by lower temperatures, if exposure last longer. Crucial 

 nature of experiments. Almost similar results with slightly higher 

 organisms. Experiments of Schwann. Value of single, properly- 

 conducted experiment with positive result. These obtained by 

 Schwann himself, and by Pouchet, Mantegazza, Wyman, and others. 

 Also by M. Pasteur. Unfair way in which the latter argues on this 

 subject. Limits of ' vital resistance ' said to be higher in neutral 

 or alkaline than in acid solutions. M. Pasteur's conclusions and 

 assumptions. 



SCIENTIFIC men are content to believe that crystals 

 may originate without the aid of pre-existing 

 crystalline matter, and it will remain for us, in sub- 

 sequent chapters, to show how far existing evidence 



