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fitted to render the phenomena more easy of apprehension by 

 our senses, without explaining them. These figurative ex- 

 pressions, with which we are so willingly and easily satisfied 

 in all sciences, are the foes of all inquiries into the mysteries 

 of nature; they are like the Fata Morgana, which show us 

 deceitful views of seas, fertile fields and luscious fruits, but 

 leave us languishing when we have most need of what they 

 promise. It is certain that the action of contagions is the 

 result of a peculiar influence dependent upon chemical forces, 

 and in no way connected with the vital principle. 77 



Liebig claimed that this poisonous substance could not be 

 isolated, because it consisted of a peculiar form of molecular 

 motion. But in many cases the substances containing this 

 molecular motion poison could be had, which substance in 

 itself was not poisonous, as was shown by exposing it to heat, 

 thus rendering it innocuous by destroying this peculiar mo- 

 lecular power. 



He also points out the fact that very many of these poisons 

 are destroyed in the human stomach in the act of digestion, 

 and that others are not. He explains these phenomena in 

 this way. All of these ferment poisons owe their power to 

 the peculiar molecular movement started and maintained by 

 the act of decomposition. Now, when they come in contact 

 with stable compounds they are unable to communicate their 

 own movements to these associated molecules, and are con- 

 sequently inert, or unable to propagate decomposition. But, 

 if the intermixed substance is composed of molecules held 

 together feebly, the molecular movement is communicated to 

 them, and they pass into a state of decomposition. 



Now the juices of the stomach are acid, and among the 

 noxious substances many are alkaline, but some are acid. 

 It therefore happens that when an alkaline organic poison or 

 ferment is introduced into the stomach, its molecular force is 



