necessary to kill Bacteria, Vibriones, §c. 



331 



ence is, moreover, thoroughly iu accordance with the broad physico-ehemi- 

 cal theory of fermentation which has been so ably expounded by Baron 

 Liebig and others, and the truth of which may now be regarded as definitely 

 established. Accordiug to this theory "living" matter, as a ferment, 

 would take rank merely as a chemical compound having a tolerably defi- 

 nite constitution ; and this, we might reasonably infer, would, like other 

 chemical compounds, be endowed with definite properties — and amongst 

 others that of being decomposed or radically altered by exposure to a certain 

 amount of heat. Looked at also from this essentially chemical point of 

 view, it would be only reasonable to expect that the molecular movements 

 of living ferments with a lowered vitality might not be more marked or 

 energetic than those which many not-living organic substances are apt to 

 undergo ; and this being the case, w T e might expect that there would often 

 be a great practical difficulty in ascertaining whether a ferment belonging 

 to the arbitrary and artificial (though, in a sense, justifiable and natural) 

 category of " living " things had or had not been in operation. 



It has, moreover, been most unmistakably proved that the limits of 

 vital resistance to heat which Bacteria, Vibriones, and their supposed 

 germs are capable of displaying are essentially the same in the three type 

 fluids which I have employed — that is, in a weak saline fluid, in a neu- 

 tral organic infusion, and in an acid organic infusion. ]So evidence exists 

 really tending to show that these organisms or their germs are capable 

 of withstanding the effects of heat better in one of such fluids than in 

 another. We may therefore safely affirm that M. Pasteur never had 

 any valid evidence in support of his conclusion that the germs of Bacteria 

 and Vibriones can resist heat better in neutral or slightly alkaline solu- 

 tions than in slightly acid mixtures. The experimental results which 

 led him to arrive at such a conclusion w r ere not logically capable of re- 

 ceiving any such interpretation, whilst they can be legitimately accounted 

 for in accordance with the broader physico-chemical theory of fermenta- 

 tion, the truth of which has now been established*. We may also 

 safely affirm that M. Pasteur's more specific statement, to the effect that 



living organisms, which M. Pasteur held (in opposition to many other chemists) to be the 

 only true ferments. In his inoculating compound (dust filtered from the atmosphere), 

 there was, as M. Pasteur was fully aware, a large amount of what his scientific opponents 

 considered not-living ferment, whilst possibly there existed a certain number of living 

 ferments. In explaining the results of his experiments, however, M. Pasteur and 

 others thought he was pursuing a logical and scientific method when he attributed these 

 results to the action of the possibly existing element of the inoculating compound, whilst 

 he ignored altogether the other element which was certainly present in comparatively 

 large quantity, and the testing of whose efficacy was the ostensible object of his research. 



* I attempted to show, nearly three years ago (see ' Mature,' July 14, 1870, pp. 224-228), 

 that, the differences which M. Pasteur ascribed to differences of vital resistance of or- 

 ganisms in particular fluids were just as explicable in accordance with the physico- 

 chemical theory of fermentation, by reference to the different degrees of fermentability 

 of the several fluids. 



