30 GRAHAM LUSK 



lay in the fact that the caloric values attributed to the oxidation of carbon 

 and hydrogen were wrong. One may compare the values used at different 

 periods as follows r 



Favre and 

 Lavoisier Despretz Silbermann 



1780 1823 1852-53 



calorie* calories calories 



1 gm. II oxidized yields. . . 22.170 23.640 34.402 

 1 gin. C oxidized yields.. . 7.237 7.914 8.080 



The agreement between Despretz and Dulong that nitrogen was 

 present in the expired air in an amount larger than that: inspired was 

 accepted for many years by many writers. Magendic, in his "Elements of 

 Physiology," in 1830, thus expresses the thoughts of his time: "Accord- 

 ing to the experiments of M. Despretz upon herbivora, the respiration 

 furnishes only 80 per cent of the animal heat, and in carnivora only 80 per 

 cent. Therefore, other sources of animal heat must exist in the economy. 

 It is probable that these occur in the friction of various parts, in the 

 movement of the blood, the friction of the blood corpuscles upon one 

 another and finally in nutritive phenomena. This supposition is not 

 forced, for it is known that most chemical combinations give rise to heat, 

 and it is doubtless true that combinations of this nature take place in the 

 organs, both during secretion and digestion.' 7 



It is evident that ignorance of the Law of the Conservation of Energy 

 hampered progress at this time. 



Dumas (1800-1884). In the year 1823 a paper was published by 

 Prevost and Dumas point ing out the fact that if the kidneys were ex- 

 tirpated in cats and rabbits, urea rose to high concentration in the blood. 

 This experiment proved that urea was not formed in the kidney. Houelle 

 in 1773 had found urea in the urine. 



It was the year 1>23. the year of the publication of the work of 

 Despretz, of Dulong and of Dumas, that Liebig, at the age of twenty, 

 came to Paris to study. This should be remembered as the story of the 

 development of the French school is unfolded. The part Liebig played 

 will be told later. 



Dumas was an organic chemist of high repute. Concerning his influ- 

 ence, the- words of Pasteur, spoken in 1882, may be recalled: "My dear 

 Master, it is indeed forty year? since I first had the happiness of knowing 

 you and since you first taught me to love science. 



"I wns fresh from the country; after each of your classes I would 

 leave the Snrbonne transported, often moved to tears. From that moment 

 your talent as a professor, your immortal labors and your noble character 

 have inspired me with an admiration which has grown' with the maturity 

 of my mind," 



