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food-materials is actually digestible ? In a piece of meat, for 

 instance, what percentage of the total protein and fats will be 

 digested by a healthy person, and what proportion of each 

 will escape digestion ? The proportions of food-constituents 

 digested by domestic animals has been a matter of active 

 investigation in the European agricultural experiment stations 

 during the past twenty years. Briefly expressed, the method 

 consists in weighing and analyzing both the food consumed and 

 the intestinal execretion, which latter represents the amount of 

 food undigested. The difference is taken as the amount 

 digested. 



Such experiments upon human subjects, however, are ren- 

 dered much more difficult by the fact that in order that the 

 digestibility of each particular food-material maybe determined 

 with certainty, we must avoid mixing it with other materials. 

 Hence the diet during the experiments must be so plain and 

 simple as to make it extremely unpalatable. An ox will live 

 contentedly on a diet of hay for an indefinite time, but for an 

 ordinary man to subsist a week on meat or fish or potatoes or 

 eggs is a very different matter. No matter how palatable such 

 a simple food may be at first to a man used to the ordinary 

 diet of a well-to-do community, it will almost certainly become 

 repugnant to him after a few days. In consequence, the diges- 

 tive functions are disturbed, and the accuracy of the trial is 

 impaired, a fact, by the way, which strikingly illustrates the 

 importance of varied diet in civilized life. For instance, in an 

 experiment conducted in the physiological laboratory at Munich, 

 by Dr. Rubner, the subject, a strong, healthy Bavarian laboring 

 man, lived for three days upon bread and water, a diet, the 

 monotony of which was much more endurable than one of meat 

 or fish or most any other single food-material would have been. 

 He was able to eat 1,185 grams (about 2 lbs. and 10 oz.) of bread 

 per day. This contained 670 grams of carbohydrates, mainly 

 starch, of which only about 538 grams, or a little less than one 

 per cent, escaped digestion. In this case, therefore, about 99 

 per cent, of the carbohydrates of the bread were digested. The 

 bread contained 13 grams of protein, of which 13 percent, were 

 undigested, and 87 per cent, or seven-eighths of the whole 



