408 SCIENTIFIC THOUGHT. 



It was supposed that the simple and well-known elements 

 of these bodies might have the property of forming 

 primarily combinations which were more firmly knit to- 

 gether than others, that these primary combinations 

 might then as it were take the place of elements and 

 act like them, forming with others of similar constitution, 

 or with the simple elements themselves, more complex 

 compounds. In these higher compounds they might 

 behave like elementary bodies, entering into and being 

 expelled from them in their own proper combinations 

 without being broken up into the ultimate elementary 

 constituents. One of the functions of the living organism 

 was by the action of the vital forces to produce these 

 primary compounds or complex atoms. It was thus 

 thought that as inorganic bodies were made up of con- 

 stituents which were elements, so organic bodies were 

 made up of constituents which were themselves partly 

 compounds. A new term had to be coined for those 

 constituents which might comprise both elementary 

 bodies and these primary compounds which behaved 

 like elements in organic substances. This was the term 

 " Eadicle." A radicle might be an element or a com- 

 pound. 1 For a long time it was thought that these 



1815), a compound of, carbon and 

 nitrogen, which was shown to behave 

 like an element. Ampere in the 

 following year showed how the salts 

 of ammonia could be brought into 

 line with the salts of other al- 

 kalies by considering them to con- 

 tain a compound element (consist- 

 ing of nitrogen and hydrogen) in 

 place of a simple element. In his 

 celebrated essay of 1818 Berzelius 

 defines organic acids as binary 

 compounds of oxygen with com- 



pound elements or radicles (Kopp, 

 ' Geschichte der Chemie,' vol. iv. p. 

 269). 



1 The term " radicle," to desig- 

 nate the principal constituent of a 

 compound, was used as far back as 

 1787 in the discussions through 

 which the French chemists reformed 

 the nomenclature of chemistry 

 (Kopp, ' Geschichte,' &c., vol. iv. 

 p. 266). It acquired a more defi- 

 nite meaning about the year 1835, 

 when Liebig, in common with Ber- 



