37S ^ NINETEENTH CENTURY. PT. ill. 



of organic chemistry , or the chemistry of Uving bodies. This 

 study began, as you will remember, when Boerhaave first 

 examined the juices of plants and the fluids in animal 

 bodies. But it can scarcely be said to have made any great 

 advance till the year 1828, when a German chemist named 

 Wohler first showed that urea, a substance in the bodies 

 of animals, can be made artificially. Since then Berthelot 

 and other eminent chemists have discovered how to make 

 many compounds in the laboratory which were before only 

 found in living beings. 



But the great master of organic chemistry whose name 

 you must remember, though we can speak but little about 

 him, was Baron Liebig, of Darmstadt, who was born in 

 1803, and died only a few years ago. He was the first to 

 analyse organic substances satisfactorily, by heating them in 

 vessels with metallic oxides, and so reducing them to carbon 

 and their other elements ; and he also brought agricultural 

 chemistry to great perfection. This subject, which was first 

 treated by Sir H. Davy, teaches how the growth of plants 

 depends upon the chemical state of the soil in which 

 tliey are sown, how different crops should be sown in suc- 

 cession in any field so as not to exhaust the soil ; and what 

 manure will best give back to the ground the elements which 

 the plants have taken out of it. Liebig also traced out the 

 changes which food undergoes in our bodies, and studied 

 which kinds turn to fat, muscle, blood, or sugar in our system. 

 In 1832 he also discovered chloroform and chlorale, though 

 these were not used for producing unconsciousness till more 

 than fifteen years later by Dr. Simpson. 



The whole history of organic chemistry, however, is far 

 beyond us at present ; the science has only existed for the 

 last fifty years, and the chemical substances which are 





