BOUSSINGAULT, DULONG, AND DESPRETZ. 915 



they live on food which contains more nitrogen 

 than is required to form blood, the excess is ex- 

 haled, as shewn by some experiments of Jurine, 

 Berthollet, Dulong, Despretz, and Nysten. Be- 

 sides, Dr. Edwards found that nitrogen was some- 

 times absorbed, and at other times ex haled, during 

 the respiration of man. 



But we are informed by Boussingault, that the 

 food of a horse living on oats and hay, contained 

 139*4 grammes of nitrogen ; whereas his excre- 

 tions during twenty-four hours, contained only 

 1 15-4 grammes of nitrogen, making an excess of 

 24 grammes in his food, and that the daily food 

 of a cow living on grass and potatoes, contained 

 20 l'5grammes, while the excretions afforded 174-5 

 of nitrogen ; making an excess of 27 grammes in 

 her food, (An. de Ch. et de Phys. Ixxi. 136.) 



But if we compare the relative quantities of 

 nitrogen in the food of herbivorous and carni- 

 vorous animals, whose blood and tissues contain 

 the same proportion of that element, it will be 

 found that the partial results of Boussingault, 

 like those of .Dulong and Despretz, cannot be true 

 as a general law of nature. For example, the 

 first two columns of the following table, exhibit 

 the proportions of solid matter and of nitrogen, 

 in different species of vegetable food, when dried 



element is deficient in the food. It is also in the lungs where blood 

 is formed, and where, after it has performed its vital office of 

 nourishing the tissues, the whole is converted into oxidized pro- 

 ducts, and other inorganic compounds. 



