PRINCIPLES OF AGRICULTURAL CHEMISTRY 



The averages of other workers are as follows: Pfeiffer 0.52 

 gm., Jordan 0.44 gm., Wolfe 0.47 gm. It appears that, on an 

 average, not more than 0.45 gm. of metabolic nitrogen (equal to 

 2.8 gm. protein) is excreted per 100 grams of digested dry mat- 

 ter. Some metabolic mineral matter is also present in the excre- 

 ment. 



Fig. 84. Stall used for digestion experiments with sheep. 

 Wyoming Station. 



Digestion Experiments. The nutrients which disappear during 

 the passage of food through the animal body are said to be 

 digested. All that disappear do not pass through the membranes 

 of the digestive organs, however, as some of them are converted 

 into marsh gas and carbon dioxide by fermentation and escape as 

 gases. The object of a digestion experiment is to determine, by 

 trials on animals, the actual amounts of the different nutrients 

 which are digested. In a digestion experiment, a known quantity 

 of food is fed, the excrement from it collected, and both food 

 and excrement are subjected to analysis. The quantity of each 

 nutrient fed and digested is calculated, and the quantity of 

 nutrient digested is divided by the quantity fed. The dividend, 

 expressed as percentages, is the coefficient of digestibility. 



