40 GRAHAM. LUSK 



persons. But this application of the method of BouBfiingault is too im- 

 perfect to establish definitely incontrovertible results in science." 



It might be added at this point that Liebig in 1845 found that nine- 

 tenths and more of the heat measured by the calorimeters of Dulong and 

 of Despretz could be accounted for from the oxidation of carbon and 

 hydrogen calculated according to the method of 'Lavoisier. The more 

 modern caloric values for hydrogen were here employed as later in 1855 

 by Gavarret. 



Liebig also points out that if one of the dogs experimented upon by 

 Dulong had really eliminated the quantity of nitrogen gas Dulong had 

 reported, the animal in seven days would have expired as nitrogen gas 

 the amount of that element contained in its hair, skin, flesh and blood, and 

 at the end of the period would have been merely a mass of mineral ash. 



Regnault (1810-1878). Henri \ r ictor Regnault was born in Aix-la- 

 chapelle, and in 1840 became professor of physics and chemistry at the 

 University of Paris. In 1847 he became also chief engineer of mines; 

 in 1854 was director of the Sevres porcelain manufactory. He was a 

 strict disciplinarian of students and up to- the outbreak of the war in 

 1914 his memory was held in tradition as representative of the highest 

 pedagogical severity. 



In 1849 Regnault and Reiset published their celebrated monograph 

 upon the respiration of animals. The apparatus which they used consisted 

 of a closed system, from which the carbonic acid produced by an animal 

 placed within the system could 'be absorbed, and into which oxygen could 

 be admitted as the atmospheric air was consumed by the animal. This is 

 the "closed system of Regnault and Reiset," the principle of which is 

 employed in modern calorimeter work (vide Atwater and Benedict, 

 1905)*. 



The results obtained were usually accurate and their interpretations 

 were within the compass of the knowledge of the time. 



Their main conclusions as they enumerated them, together with some 

 of trrek^experimental data, are presented in the following abstract : 



For anrrna-k. of warm blood, mammals and birds: 



1. Normally nourished animals constantly expire nitrogen but the 

 quantity eliminated is very small, never exceeding two per cent and often 

 being less than one per cent of the total oxygen consumption. 



2. If animals fast they 'frequently absorb nitrogen. The proportion 

 of nitrogen absorbed varies within the same limits as the exhalation of 

 nitrogen by animals regularly fed. This absorption of nitrogen takes 

 place in almost every instance in the case of birds but scarcely ever *in 

 mammals. . . . 



(In experiment 10 performed on a rabbit the quantity of nitrogen 

 absorbed was 0.08 per cent of the quantity of oxygen absorbed. In the 

 text of the article they remark that the enormous elimination of nitrogen 



