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1892. ] NEW YORK ACADEMY OF SCIENCES. 111 
of these elements differ from those with which inorganic nature 
presents us.” 
In other cases the chemists of that time believed in the action of 
what they called a vital force, which acted in the formation of 
organic compounds and not in the case of inorganic compounds. 
They said it is easy to take organic substances to pieces and resolve 
them into simpler compounds, but to build them up from their ele- 
ments was an impossibility without the intervention of vital force. 
Thus we could convert the complex substance grape-sugar into 
alcohol and carbon dioxide, but it took vital force to make the sugar 
in the grapes and other vegetable substances that contain it. 
The first good blow against the vital-force theory was struck in 
1828, when Wobler succeeded in making urea artificially by boiling 
an alcoholic solution of ammonium cyanate, thus from purely inor- 
ganic materials building up a substance as truly organic as any we 
ean find in the animal or vegetable kingdoms; but even this master- 
stroke of a master-hand did not at once overthrow the theory of 
vital force, although the best minds in the chemical world saw its 
power and the tendencies of the researches that would be made in 
the future. . 
Liebig, Berzelius, Dumas, and Boullay all worked upon organic 
bodies with a view to determine their constitution. The constitu- 
tion of oil of bitter almonds, discovered by Liebig and Wohler; the 
discovery of ethyl in alcohol by Berzelius and Liebig ; the formation 
of aldehyde and acetic acid; formic acid from methyl alcohol or 
wood-spirit ; the discovery by Liebig of chloride of methenyl or 
chloroform, and also chloral, all followed as the early fruits of this 
organic research. 
‘And while we are talking of Liebig, it is interesting to note that 
his father was a wholesale druggist, and his own first ‘knowledge of 
chemistry began while he was an apprentice to an apothecary at 
Heppenheim, near Darmstadt. It was in this position that he made 
some of his first experiments upon the fuilminates, and having the 
misfortune to cause a great explosion his term of apprenticeship 
was soon ended. Liebig afterward made a number of interesting 
contributions to chemical knowledge. It was he that obtained 
picric acid from aloes, although aloin was not discovered and iso- 
lated until more recently. In 1829 Liebig discovered hippuric acid ; 
but the work that made. him most famous was his improvements 
in the methods of organic analysis In old times when a chemist 
wished to find out what a substance contained he put it into a retort 
and heated it, or, as we say, subjected it to dry distillation He 
then obtained a watery liquid, afterward some oily matters, and 
an alkali in the case of animal substances, which he soon learned 
was ammonia; but there were also obtained certain gases which 
he did not collect, and a mass of carbon remained in the retort. 
But Liebig had learned that organic bodies contained carbon, 
hydrogen, oxygen, and nitrogen, “and he perfected the methods 
