456 CHEMICAL DISCOVERY AND INVENTION 



enzymes separated from trie living tissue in which they were 

 generated. It is usually assumed that their activity and mode of 

 action is the same in the parent tissue, but this assumption, 

 however probable, is incapable of strict verification. In any 

 case it is a matter for further research to what extent the pro- 

 cesses of absorption and assimilation, of growth and develop- 

 ment are wholly dependent on these catalytic processes, or are 

 at least partly the result of still more complex changes wrought 

 by the living protoplasm itself. 



CHAPTER XXXII 



ORGANIC CHEMISTRY 



IN previous chapters an account has been given of some of 

 the more important constituents of animals and vegetables and 

 of the definite products of secretion. The study of such sub- 

 stances as sugar or colouring matters was formerly called, perhaps 

 not altogether improperly, organic chemistry, as an abbreviated 

 expression meaning the chemistry of organised beings. Such 

 compounds as those mentioned and many others were supposed 

 to be producible only by living things through the agency of 

 what was called vital force. 



The expression " organic " chemistry has become established 

 by long usage, and it seems impossible to get rid of it, but it 

 should be remembered that the customary application to the 

 chemical history of all the multitudinous hydrocarbons, alcohols, 

 acids, bases, sugars, etc., etc., is not intended to imply that there 

 is any difference in the fundamental principles of organic and 

 inorganic or mineral chemistry. A very large number of the 

 known definite organic compounds, in which carbon is the 

 characteristic central element, can now be produced by purely 

 artificial processes in the chemical laboratory, independently of 

 any operation in which plant or animal life is concerned. A 

 considerable number of examples have been mentioned in the 

 earlier pages of the book, and especially in the recent chapters. 

 The history of organic synthesis may be said to have begun in 

 1828 when Wohler observed the change of ammonium cyanate 

 into urea and, though not ended, may be said to have culminated 

 in the methods by which Emil Fischer has built up the complex 

 molecules of some of the proteins. 



