ON THE BACTERIA. 151 



or that I wish to hmit the power of matter in relation to life. My 

 views on this subject ought to be well known. But possibility 

 is one thing, and proof is another ; and when in our day I seek 

 for experimental evidence of the transformation of the non-living 

 into the living, I am led inexorably to the conclusion that no such 

 evidence exists, and that in the lowest, as in the highest of 

 organised creatures, the method of Nature is, that life shall be the 

 issue of antecedent life." '^ 



As to the actual part played by the Bacteria in putrefaction, 

 we again find ourselves on debateable ground. We may take it 

 for granted that no decomposition takes place without their being 

 present ; the disputed point is whether their connection with the 

 process is only accidental, or whether they are the actual cause of 

 the phenomenon. The Heterologists, or advocates of Spontane- 

 ous Generation, say that the molecules of a putrefying body are 

 in a state of motion tending to the disruption of their elements, 

 and that the Bacteria are not the cause of this so-called inoto7'- 

 decay, but that they are the result of the contact of non-living 

 elements in this condition, with the physical forces of the 

 atmosphere in relation with them. Their opponents (on the 

 contrary) say that the organic elements of a putrescible compound 

 undergo disruption by no inherent tendency of their own, but 

 that putrefaction is directly occasioned by the influence upon them 

 of these living, growing, and multiplying organisms ; whether they 

 generate a ferment which produces this effect, or whether they do 

 so by their very acts of life and growth. 



Perhaps, in the present state of our knowledge, it is better not 

 to attempt too precise a definition on the subject. There is, 

 however, no doubt that, in the absence of Bacteria, putrefaction 

 is a very slow process, and we may therefore conclude that, even 

 if they do not originate the process, they immensely hasten it : so 

 that it is owing to these infinitely minute agents that the transfor- 

 mation of dead organic matter, into matter suitable to take its 

 place in the general current of natural processes, is hastened and 

 completed, and an equilibrium maintained between the organic 

 and the inorganic world : and it is not too much to say that it is 



* Tyndall's Paper at the Royal Institution, June 8, 1877. 



