Polytechnic Association. 577 



opposing parties in the learned societies of France, who have long 

 mooted the question- as to the cause of putrefaction and fermentation, 

 and who appear to have arrived at that stage at which each prefers to 

 remain unconvinced. In both processes there is observed the occur- 

 rence, growth and multiplication of living organisms, either amid the 

 particles of the moist decomposing substance, or upon the surface, 

 where these frequently make their appearance as ordinary mildew. 

 How are these results explained by the two theories ? According to 

 the one, the molecules of a putrefying or fermenting body are in a 

 state of motion, tending to the disruption of their elements. The 

 living particles observed are the results of the communion of certain 

 non-living elements with the physical forces with which they are in 

 relation. Thus there is a strict analogy between crystallization and 

 creation. As in the one case certain molecules, under certain condi- 

 tions, assume definite crystalline forms, so certain molecules under 

 other conditions assume the appearances and attributes of vitality. 

 According to the other theory, there is a single cause for all the phe- 

 nomena. This cause is the presence of living matter. The organic 

 elements of a putrescible or fermentable compound undergo disrup- 

 tion by no inherent tendency of their particles to motion, but by the 

 influence upon them of living, growing and multiplying organisms 

 which, by their very acts of life and struggle for existence, superin- 

 duce this disruption. The living beings which are acknowledged to 

 be present arc the intimate causes, and not the adventitious signs, nor 

 yet merely intermediate agents, of the decomposition of the material. 

 Dr. Sansom investigates the question from the stand-point of the 

 second theory. After presenting the principal positions which have 

 been established by experiment and observation, he takes up the only 

 real objection to the reception of the germ theory — the resistance to 

 the destructive agency of heat — and then alludes to the defects of 

 other physical agencies which may contribute to a solution of the 

 question. It is not by the results of a single method of investigation 

 that this question is to be judged, but rather by the collective evidence 

 of many methods. 



Heat is not the only destructive agency which may be employed in 

 the inquiry ; others, fraught with much valuable teaching, may be 

 put in force, though these have been apparently in the recent contro- 

 versies entirely ignored. Such are the evidences derived from the 

 destructive influences of chemical and of poisonous agents. It has 

 been known from time immemorial that the addition of certain com- 

 pounds prevents both putrefaction and fermentation. The belief being 

 [Inst.] 37 . 



