A HISTORY OF METABOLISM 45 



"Attracted to Paris by the immense reputation of those celebrated masters 

 whose glorious researches established the foundations of the sciences and elevated 

 them into an admirable edifice, he had no other introduction to you except his 

 love of study and his fixed desire to profit from your teachings. 



"You bestowed on him a most encouraging and flattering welcome, you 

 directed his first researches, and through your influence he had the honor to 

 communicate them to the Academic. 



"It was the session of the 28th of July which decided his future and opened 

 a career in which for seventeen years he has labored to justify your benevolent 

 patronage. 



"If his labors have been useful, it is to you that science is indebted for 

 them, and he feels obliged to express publicly to you his ineffaceable sentiments 

 of -gratitude, esteem and veneration." 



JUSTUS LIEBIG. 

 Giessen, 1 January, 1841. 



Through the influence of Alexander von Humboldt, Liebig was ap- 

 pointed professor of chemistry at Giessen in 1824 at the age of twenty- 

 one. Wilhelm Ostwald writes in his "Grosse Manner" that this gave 

 him free water to swim in. Here he built the first modern chemical re- 

 search laboratory and attracted to it men, many of whom afterward became 

 distinguished. Liebig's "Thierchemic in Ihrer Anwendung auf Physiol- 

 ogie und Pathologie" was first published in 1840 and passed through nine 

 editions. Comparison should be made between it and the publications 

 of Boussingault already described. 



Liebig divided the foodstuffs into protein, fat and carbohydrate, and 

 stated that protein could take the place of body protein, while carbo- 

 hydrate and fat could spare body fat. He believed that muscular work 

 caused the metabolism of protein, while oxygen destroyed fat and car- 

 bohydrate. 



In the introduction he states that in fifty years it will be as impossible 

 to separate chemistry from physiology as it was then to separate chemistry 

 from physics; that he had endeavored to bring chemistry and physiology 

 together in a single book. 



In one of his writings Liebig says that the acceptance of principles, 

 like the application of chemistry to physiology, all depends on the mental 

 development, that the great Leibnitz refused to accept Newton's doctrine 

 of gravitation, which is now understood by every schoolboy. 



The time was propitious for the writing of Liebig's book. He himself 

 had been more largely the creator of organic chemistry than any man then 

 living. Chemical compounds of carbon were becoming known. Scheele 

 had discovered uric acid and lactic acid in 1776 and glycerin as a com- 

 ponent of fat in 1778; Fourcroy and Vauquelin in 1779 and Prout in 

 1803 had analyzed urea; Chevreul announced the chemical constitution of 

 fat in 1823 and Thenard investigated the composition of bile; Berzelius, 

 the composition of the secretions in general. In 1828 Wohler prepared 



