38 GRAHAM LUSK 



2211 263 1952 27 +32 



Uniting the oxygen of the food with the hydrogen in such a proportion 

 as to form water, there would remain 19.8 gm. of hydrogen requiring 

 inspired atmospheric oxygen for its conversion into water. The loss of 

 carbon equaling 2211 gm., it would require 4052 liters to convert it into 

 7999 gm. of carbonic acid. A cow would therefore deprive 19 square 

 meters of air of its oxygen. 



Boussingault states that one nitrogen determination is not sufficient 

 to decide whether nitrogen as a gas enters into the metabolism of 

 protein. 



The same kind of work is done with a horse (Boussingault, (a) 1839). 

 It is concluded that 4584 liters of oxygen would be required to form the 

 carbonic acid produced. There were 24 gm. less of nitrogen in the 

 excreta than in the food. It seems clear that atmospheric nitrogen is not 

 assimilable by the body. 



In a subsequent experiment published in 1843 Boussingault (c) gives 

 food to a turtle-dove and estimates the carbonic acid elimination as he 

 had done with the horse, but he also determines directly the carbonic acid 

 given off. By the first method 0.211 gm. of carbon were estimated to 

 have been expired and by the second method an average of 0.198 gm. 

 were actually found. This closely approaches modern technic. 



Boussingault and Le Bel (1839) made the first complete analyses 

 of cow's milk. They conclude from their -work that the nature of the 

 fodder does not affect the quantity or the chemical composition of the 

 milk, provided the cow receives the same relative nutritive equivalents in 

 the fodder. 



The nutritive equivalents, however, were based on the nitrogen content 

 of the fodders, thus 13.5 kg. of hay were accounted the nutritive equiva- 

 lents of 54 kg. of beets or 27 kg. of potatoes. It is evident that at this 

 date there was no real understanding of the nature of the different food- 

 stuffs. 



Barral (1819-1884) in 1849 applied the principles of Boussingault's 

 method to the analysis of the metabolism of human beings. He thus 

 presents his problem: "Knowing the amount and the elementary com- 

 position of the food, both solid and liquid, taken each day, determining 

 the elementary composition of the excreta and perspiration, one may 

 calculate the gains and losses of the human body." 



His experiment on himself lasted five days, with the following results 

 per day: 



