302 



PRINCIPLES OF GENERAL PHYSIOLOGY 



compounds formed, but remain unaltered ; they are stated to act by an " indwelling 

 force, whose nature is still unknown." Shortly before Thenard's discovery, 

 Humphrey Davy had found that platinum, under certain conditions, had the 

 power of causing the oxidation of alcohol vapour in air. Edmund Davy, his 

 cousin, made a more active preparation, which was actually platinum in a very 

 finely divided state, and Dtibereiner made a spongy platinum which could even 

 cause the union of oxygen and hydrogen gases. As we shall see later, this 

 greater activity is due to the greater extent of surface. Berzelius points out 



that this property is 

 not confined to 

 platinum, but, in a 

 less degree, is pos- 

 sessed by other sub- 

 stances. Thus, while 

 platinum is active 

 even below C., gold 

 requires a higher 

 temperature, silver 

 still higher, and glass 

 at least 300. He 

 next refers to the 

 phenomena of alco- 

 holic fermentation, 

 known since the 

 earliest times, before 

 written history. 

 But, until Cagniard 

 de Latour (1838), the 

 fact that it was pro- 

 duced by a living 

 organism was un- 

 known. The words 

 used by Berzelius are 

 worth quoting: "We 

 had made acquaint- 

 ance with the fact 

 that, for example, the 

 change of sugar into 

 carbonic acid and 

 alcohol takes place in 

 fermentation under 

 the influence of an 

 insoluble body, which 

 we call 'ferment,' 

 and also with the 

 fact that this ferment 

 could be replaced, 

 although less effec- 

 tively, by animal fibrin, coagulated plant albumin, cheese and similar substances, as 

 well as with the experience that the process could not be explained by a chemical 

 action between the sugar and the ferment analogous to double decomposition. 

 Comparing it with known relations in the inorganic world, it was seen to be 

 most like the decomposition of hydrogen peroxide under the influence of platinum, 

 silver, or fibrin ; it was, therefore, natural to suppose that the action of the 

 ferment was an analogous one." The investigations of Mitscherlich on the 

 formation of ether from alcohol by sulphuric acid are next brought into connection 

 with those of Kirchhof on sugar and with the action of alkalies in decomposing 

 hydrogen peroxide. What is common to all is the manifestation of a "new 

 force," different from chemical affinity in the ordinary meaning of the words, 



FIG. 82. PORTRAIT OF BERZELIUS. 



(From the painting by Sodermark. ) 



