A HISTORY OF METABOLISM . 37 



Dumas came into frequent intellectual conflict with Liebig and 

 \Yohler in Germany and Berzelius in Sweden. In 1828 Wohler produced 

 urea synthetically from ammonium cyanate, delivering the final death 

 Mow to the doctrine that organic compounds arise only through the inter- 

 vention of living things. 



IVIagendie (1780-1855) was among the first to differentiate between 

 various kinds cf foods. This distingiiisttcc.1 physiologist fed doii's cane 

 .sugar or olive oil or butter and found tliat death occurred in 31 davs 

 < Magendie, 183(>). He rightly concluded that the nitrogen of the organs 

 of the body arose only from the nitrogen <; the food, that the nitrogen-free 

 food-stuffs were not transformable into nitrogen-containing food-stuffs. 

 He rendered great service in pointing out the nitrogen content of rice, 

 maize and potatoes, foods upon which people live. 



Magendie also found that dogs fed with bread alone lived only a 

 month. The second gelatin commission of the French Academy (Magen- 

 die, 1841), sitting in 1841 under the presidency of Magendie, determined 

 that bread and gelatin given together to either dog or man constituted an 

 insufficient diet. 



Boussingault (1802-1887). Organic analysis, which was founded by 

 Lavoisier, was further advanced by Gay-Lns'sac and Thcnard (1810-15), 

 by Berzelius in 1814, and was perfected hy Liebig in 1830. This work 

 led to that of Boussingault, who curiously enough had been previously for 

 several years in the employ of an English mining company in equatorial 

 South America. 



The experiments of Boussingault in 1839 may be considered to be 

 prophetic of the future evolution of metabolism studies. Boussingault 

 compares the quantities of carbon, hydrogen, nitrogen and oxygen in the 

 fodder constituting a maintenance ration of a milch cow, with the quan- 

 tities of the same elements eliminated in the urine, feces and milk. The 

 difference between these quantities \vcmld fce available for the respiration. 

 He gives the following account ( Boitssangaiilt, (I) 1830) : 



''It is generally recognized to-day that the food of animals must con- 

 tain a certain amount of nitrogen. The presence of nitrogen in a large 

 number of vegetable foods forces the* conclusion that herbivora receive 

 nitrogen in their food, which enters into their constitution. 



"In ordinary alimentation an -individual does not change his average 

 weight; this state of affairs exists when an animal takes a maintenance 

 ration (ration d'entretieri)" 



Under these conditions the food of the animal should be found in his 

 excretions. During growth, or the |nx3cess of fattening the conditions 

 would be different. 



Cows were given a maintenance ration of known elementary com- 

 position and the elements recovered in the urine, feces and milk were 

 subtracted from those in the fodder, with the following results: 



