CHAPTER XVIII 



THE ELEMENTS AND WATER, IN RELATION 

 TO THE LIFE-WORLD 



I HAVE already (in Chapter XVI.) given the statements of 

 two continental physiologists as to the great chemical complex- 

 ity of the proteid molecule, involving as it does, in certain 

 cases already studied, a combination of about two thousand 

 chemical atoms. A more recent authority (Mr. W. Bate 

 Hardy) is of opinion that this molecule really contains 

 about thirty thousand atoms, while the most complex 

 molecule known to the organic chemist is said to contain 

 less than a hundred. One of the results of this extreme 

 complexity is that almost all the products of the vegetable 

 and animal kingdoms are what are termed hydro-carbons, 

 that is, they consist of compounds of carbon, with hydrogen, 

 oxygen, or nitrogen, or any or all of them, combined in an 

 almost infinite variety of ways. Yet the compounds of these 

 four elements already known are more numerous than those 

 produced by all the other elements, more than seventy in 

 number. 



This abundance is largely due to the fact that the very 

 same combination of carbon with the three gaseous con- 

 stituents of the carbon-compounds often produces several 

 substances very different in appearance and properties. 

 Thus dextrine (or British gum), starch, and cellulose (the 

 constituents of the fibres of plants) all consist of six atoms 

 of carbon, ten of hydrogen, and five of oxygen ; yet they 

 have very different properties, cellulose being insoluble in 

 water, alcohol, or ether ; dextrine soluble in water but not 

 in alcohol ; while starch is only soluble in warm water. 

 These differences are supposed to be due to the different 



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