THE ATOMIC VIEW OF NATURE. 



409 



complex radicles, as distinguished from the elements, 

 were produced mainly if not exclusively in the organ- 

 ism of the plant or of the animal. Liebig himself, who is. 



Liebig's de- 



favoured this view, and who first brought organic chem- finitionof 



" ^ organic 



istry in its application to agriculture and physiology chemistry. 

 under the notice of a large circle of readers, introduced 

 this branch of the subject with the designation of the 

 chemistry of compound radicles, inorganic or mineral 

 chemistry being termed the chemistry of simple radicles. 

 The radicles were, according to Liebig, the true elements 

 of organic chemistry. The binary system of Berzelius 

 received another attack led by the celebrated French 

 chemists Laurent and Gerhardt, with whom Dumas tem- 

 porarily allied himself. It was about the year 1840 that 

 the idea of " substitution " entered the list of formulae 

 by which chemical philosophers attempted to systematise tio" 

 and simplify the ever-growing number of definite com- 

 pounds, supplied mainly by organic analysis.'^ It was 



19. 



Substitu- 



zelius and with Dumas, established 

 what is now called the older radicle- 

 theory of organic compounds. As 

 Kopp has shown (' Entwiekelung 

 der Chemie, p. 576, &c. ), it remained 

 undecided at that time whether 

 these organic radicles had actual 

 existence, or whether they were 

 merely a convenient symbolism, 

 whether they could be isolated, like 

 cyanogen, or whether they existed 

 only in combinations, whether 

 they were fixed and unchangeable, 

 or whether they could themselves 

 be converted one into another, 

 whether the same compound could 

 be referred for convenience sake 

 to more than one constituent rad- 

 icle. " By most chemists the defini- 

 tion of organic chemistry given by 

 Liebig ('Organic Chemistry,' 1843) 



was adopted, that it was the chem- 

 istry of compound radicles ; . . . 

 that these radicles really existed 

 in the compounds as definite con- 

 stituents ; and if it was then said 

 that these radicles were mostly 

 hypothetical, this was understood 

 as meaning that some of them were 

 known in the free state, others not " 

 (p. 581). 



^ Even before that time the views 

 of many eminent chemists had been 

 greatly influenced by the discoveries 

 and experiments of two great na- 

 tural philosophers of this country 

 who kept themselves free from the 

 theoretical considerations which had 

 led Berzelius in the elaboration of 

 his electro-chemical and binary sys- 

 tem. These were the researches of 

 Davy regarding the so-called hydro- 



