DIGESTION 



399 



With men, the faeces from different meals are not mixed in 

 the body, and can easily be separated by appropriate means. 

 Thus, at the meal before beginning the experiment, the man 

 swallows a capsule of charcoal. Then for two or three days he 

 eats the ration to be tested. At the end of the period he takes 

 another capsule of charcoal. The dividing line between excre- 

 ments from the meal without charcoal and the one with charcoal, 

 is easily distinguished, and the excrement from the ration tested 

 can be separated easily. 



Fig. 85. Sheep arranged for digestion experiment. Wyoming Station. 



With domestic animals, the food from different meals is mixed 

 so thoroughly in the stomach and intestines that not only is it im- 

 possible to distinguish one meal from another, but the residues 

 from a given meal may appear in the excrement for three or 

 four days. Such animals are fed a uniform quantity of food 

 long enough to ensure the elimination of previous food residues, 

 and the excrement is collected for a definite number of days. It 



