j> ^Appendix. 



well-grounded philosophy or of fallacious hypothesis appertains 

 has, in no small share, been due to work which has been skep- 

 tically designated as that of " those German chemists running 

 crazy with what they call their aromatic group." It is not to be 

 supposed that the expenditure of this labor, or of any pioneer 

 labor in science, has been without waste. But the evidence of 

 its substantial success is before the chemical world in the long 

 list of well-defined aromatic bodies now as truly under the con - 

 trol of the chemist, in analysis and in synthesis, as are the metal- 

 lic salts. And this evidence is not addressed to the chemical 

 world alone. The world of factories and ships, the world seek- 

 ing a sign as to the truth and use of all and any science, has re- 

 ceived from the chemistry of the aromatic group a good number 

 of palpable demonstrations of the power of chemical knowledge. 

 There have been produced, under chemical direction, from fhe 

 waste of coal-gas manutacture alone, aromatic substances as fol- 

 lows : since 1856, anilin dyes, now sold at ten millions of dol- 

 lars yearly, to color stuffs in the tints of the rainbow for every 

 household; since 1870, madder dye, amounting in 1873, to 

 1,000 tons, valued at over four millions of dollars ; and, this year, 

 the acid of wintergreen oil, promising to be the most useful of 

 the antiseptics, being applicable to foods and drinks, beside a 

 considerable number of other products, in themselves of no 

 slight importance in commerce and the arts. Assuredly, the aro- 

 matic bodies have been found valuable material both in physical 

 science and in industrial economy. 



As regards their significance in biological science, the ques- 

 tion will arise : how far may an insight into the constitution of 

 molecules formed in plants help the chemist toward an under- 

 standing of the formative steps in plant chemistry? Before we 

 can reach this final question in our subject, we must consider, 

 first, what the aromatic group is and where in the vegetable 

 kingdom it extends, and, next, by what steps the molecules of this 

 group are formed outside of living bodies, under conditions ar- 

 ranged by the chemist. 



The aromatic group, when this term was first adopted, con- 

 sisted of benzoic acid, bitter almond oil, amygdalin, cinnamic 



